5fa082b1f8
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2643 lines
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<!DOCTYPE article PUBLIC "-//FreeBSD//DTD DocBook V4.1-Based Extension//EN" [
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<!ENTITY % articles.ent PUBLIC "-//FreeBSD//ENTITIES DocBook FreeBSD Articles Entity Set//EN">
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%articles.ent;
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]>
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<article>
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<articleinfo>
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<title>Storage Devices</title>
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<authorgroup>
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<author>
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<firstname>Wilko</firstname>
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<surname>Bulte</surname>
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<affiliation>
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<address><email>wilko@FreeBSD.org</email></address>
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</affiliation>
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</author>
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</authorgroup>
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<pubdate>$FreeBSD$</pubdate>
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<legalnotice id="trademarks" role="trademarks">
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&tm-attrib.freebsd;
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&tm-attrib.general;
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</legalnotice>
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<abstract>
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<para>This article talks about storage devices with FreeBSD.</para>
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</abstract>
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</articleinfo>
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<sect1 id="esdi">
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<title>Using ESDI hard disks</title>
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<para><emphasis>Copyright © 1995, &a.wilko;. 24 September
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1995.</emphasis></para>
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<para>ESDI is an acronym that means Enhanced Small Device
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Interface. It is loosely based on the good old ST506/412
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interface originally devised by Seagate Technology, the makers
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of the first affordable 5.25" winchester disk.</para>
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<para>The acronym says Enhanced, and rightly so. In the first
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place the speed of the interface is higher, 10 or 15
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Mbits/second instead of the 5 Mbits/second of ST412 interfaced
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drives. Secondly some higher level commands are added, making
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the ESDI interface somewhat <quote>smarter</quote> to the operating system
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driver writers. It is by no means as smart as SCSI by the way.
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ESDI is standardized by ANSI.</para>
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<para>Capacities of the drives are boosted by putting more sectors
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on each track. Typical is 35 sectors per track, high capacity
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drives I have seen were up to 54 sectors/track.</para>
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<para>Although ESDI has been largely obsoleted by IDE and SCSI
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interfaces, the availability of free or cheap surplus drives
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makes them ideal for low (or now) budget systems.</para>
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<sect2>
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<title>Concepts of ESDI</title>
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<sect3>
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<title>Physical connections</title>
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<para>The ESDI interface uses two cables connected to each drive.
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One cable is a 34 pin flat cable edge connector that carries the
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command and status signals from the controller to the drive and
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vice-versa. The command cable is daisy chained between all the
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drives. So, it forms a bus onto which all drives are
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connected.</para>
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<para>The second cable is a 20 pin flat cable edge connector that
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carries the data to and from the drive. This cable is radially
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connected, so each drive has its own direct connection to the
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controller.</para>
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<para>To the best of my knowledge PC ESDI controllers are limited to
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using a maximum of 2 drives per controller. This is compatibility
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feature(?) left over from the WD1003 standard that reserves only a
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single bit for device addressing.</para>
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</sect3>
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<sect3>
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<title>Device addressing</title>
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<para>On each command cable a maximum of 7 devices and 1 controller
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can be present. To enable the controller to uniquely identify
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which drive it addresses, each ESDI device is equipped with
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jumpers or switches to select the devices address.</para>
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<para>On PC type controllers the first drive is set to address 0,
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the second disk to address 1. <emphasis>Always make
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sure</emphasis> you set each disk to an unique address! So, on a
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PC with its two drives/controller maximum the first drive is drive
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0, the second is drive 1.</para>
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</sect3>
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<sect3>
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<title>Termination</title>
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<para>The daisy chained command cable (the 34 pin cable remember?)
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needs to be terminated at the last drive on the chain. For this
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purpose ESDI drives come with a termination resistor network that
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can be removed or disabled by a jumper when it is not used.</para>
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<para>So, one and <emphasis>only</emphasis> one drive, the one at
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the farthest end of the command cable has its terminator
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installed/enabled. The controller automatically terminates the
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other end of the cable. Please note that this implies that the
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controller must be at one end of the cable and
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<emphasis>not</emphasis> in the middle.</para>
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</sect3>
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</sect2>
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<sect2>
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<title>Using ESDI disks with FreeBSD</title>
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<para>Why is ESDI such a pain to get working in the first
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place?</para>
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<para>People who tried ESDI disks with FreeBSD are known to have
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developed a profound sense of frustration. A combination of factors
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works against you to produce effects that are hard to understand
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when you have never seen them before.</para>
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<para>This has also led to the popular legend ESDI and FreeBSD is a
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plain NO-GO. The following sections try to list all the pitfalls
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and solutions.</para>
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<sect3>
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<title>ESDI speed variants</title>
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<para>As briefly mentioned before, ESDI comes in two speed flavors.
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The older drives and controllers use a 10 Mbits/second data
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transfer rate. Newer stuff uses 15 Mbits/second.</para>
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<para>It is not hard to imagine that 15 Mbits/second drive cause
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problems on controllers laid out for 10 Mbits/second. As always,
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consult your controller <emphasis>and</emphasis> drive
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documentation to see if things match.</para>
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</sect3>
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<sect3>
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<title>Stay on track</title>
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<para>Mainstream ESDI drives use 34 to 36 sectors per track. Most
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(older) controllers cannot handle more than this number of
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sectors. Newer, higher capacity, drives use higher numbers of
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sectors per track. For instance, I own a 670 MB drive that has 54
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sectors per track.</para>
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<para>In my case, the controller could not handle this number of
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sectors. It proved to work well except that it only used 35
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sectors on each track. This meant losing a lot of disk
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space.</para>
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<para>Once again, check the documentation of your hardware for more
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info. Going out-of-spec like in the example might or might not
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work. Give it a try or get another more capable
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controller.</para>
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</sect3>
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<sect3>
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<title>Hard or soft sectoring</title>
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<para>Most ESDI drives allow hard or soft sectoring to be selected
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using a jumper. Hard sectoring means that the drive will produce
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a sector pulse on the start of each new sector. The controller
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uses this pulse to tell when it should start to write or
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read.</para>
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<para>Hard sectoring allows a selection of sector size (normally
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256, 512 or 1024 bytes per formatted sector). FreeBSD uses 512
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byte sectors. The number of sectors per track also varies while
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still using the same number of bytes per formatted sector. The
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number of <emphasis>unformatted</emphasis> bytes per sector
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varies, dependent on your controller it needs more or less
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overhead bytes to work correctly. Pushing more sectors on a
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track of course gives you more usable space, but might give
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problems if your controller needs more bytes than the drive
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offers.</para>
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<para>In case of soft sectoring, the controller itself determines
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where to start/stop reading or writing. For ESDI hard sectoring
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is the default (at least on everything I came across). I never
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felt the urge to try soft sectoring.</para>
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<para>In general, experiment with sector settings before you install
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FreeBSD because you need to re-run the low-level format after each
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change.</para>
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</sect3>
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<sect3>
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<title>Low level formatting</title>
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<para>ESDI drives need to be low level formatted before they are
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usable. A reformat is needed whenever you figgle with the number
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of sectors/track jumpers or the physical orientation of the drive
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(horizontal, vertical). So, first think, then format. The format
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time must not be underestimated, for big disks it can take
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hours.</para>
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<para>After a low level format, a surface scan is done to find and
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flag bad sectors. Most disks have a manufacturer bad block list
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listed on a piece of paper or adhesive sticker. In addition, on
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most disks the list is also written onto the disk. Please use the
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manufacturer's list. It is much easier to remap a defect now than
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after FreeBSD is installed.</para>
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<para>Stay away from low-level formatters that mark all sectors of a
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track as bad as soon as they find one bad sector. Not only does
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this waste space, it also and more importantly causes you grief
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with bad144 (see the section on bad144).</para>
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</sect3>
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<sect3>
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<title>Translations</title>
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<para>Translations, although not exclusively a ESDI-only problem,
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might give you real trouble. Translations come in multiple
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flavors. Most of them have in common that they attempt to work
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around the limitations posed upon disk geometries by the original
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IBM PC/AT design (thanks IBM!).</para>
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<para>First of all there is the (in)famous 1024 cylinder limit. For
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a system to be able to boot, the stuff (whatever operating system)
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must be in the first 1024 cylinders of a disk. Only 10 bits are
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available to encode the cylinder number. For the number of
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sectors the limit is 64 (0-63). When you combine the 1024
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cylinder limit with the 16 head limit (also a design feature) you
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max out at fairly limited disk sizes.</para>
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<para>To work around this problem, the manufacturers of ESDI PC
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controllers added a BIOS prom extension on their boards. This
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BIOS extension handles disk I/O for booting (and for some
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operating systems <emphasis>all</emphasis> disk I/O) by using
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translation. For instance, a big drive might be presented to the
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system as having 32 heads and 64 sectors/track. The result is
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that the number of cylinders is reduced to something below 1024
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and is therefore usable by the system without problems. It is
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noteworthy to know that FreeBSD does not use the BIOS after its
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kernel has started. More on this later.</para>
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<para>A second reason for translations is the fact that most older
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system BIOSes could only handle drives with 17 sectors per track
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(the old ST412 standard). Newer system BIOSes usually have a
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user-defined drive type (in most cases this is drive type
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47).</para>
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<warning>
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<para>Whatever you do to translations after reading this document,
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keep in mind that if you have multiple operating systems on the
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same disk, all must use the same translation</para>
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</warning>
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<para>While on the subject of translations, I have seen one
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controller type (but there are probably more like this) offer the
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option to logically split a drive in multiple partitions as a BIOS
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option. I had select 1 drive == 1 partition because this
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controller wrote this info onto the disk. On power-up it read the
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info and presented itself to the system based on the info from the
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disk.</para>
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</sect3>
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<sect3>
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<title>Spare sectoring</title>
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<para>Most ESDI controllers offer the possibility to remap bad
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sectors. During/after the low-level format of the disk bad
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sectors are marked as such, and a replacement sector is put in
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place (logically of course) of the bad one.</para>
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<para>In most cases the remapping is done by using N-1 sectors on
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each track for actual data storage, and sector N itself is the
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spare sector. N is the total number of sectors physically
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available on the track. The idea behind this is that the
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operating system sees a <quote>perfect</quote> disk without bad sectors. In
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the case of FreeBSD this concept is not usable.</para>
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<para>The problem is that the translation from
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<emphasis>bad</emphasis> to <emphasis>good</emphasis> is performed
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by the BIOS of the ESDI controller. FreeBSD, being a true 32 bit
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operating system, does not use the BIOS after it has been booted.
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Instead, it has device drivers that talk directly to the
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hardware.</para>
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<para><emphasis>So: do not use spare sectoring, bad block remapping
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or whatever it may be called by the controller manufacturer when
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you want to use the disk for FreeBSD.</emphasis></para>
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</sect3>
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<sect3>
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<title>Bad block handling</title>
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<para>The preceding section leaves us with a problem. The
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controller's bad block handling is not usable and still FreeBSD's
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filesystems assume perfect media without any flaws. To solve this
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problem, FreeBSD use the <command>bad144</command> tool. Bad144
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(named after a Digital Equipment standard for bad block handling)
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scans a FreeBSD slice for bad blocks. Having found these bad
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blocks, it writes a table with the offending block numbers to the
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end of the FreeBSD slice.</para>
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<para>When the disk is in operation, the disk accesses are checked
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against the table read from the disk. Whenever a block number is
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requested that is in the <command>bad144</command> list, a
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replacement block (also from the end of the FreeBSD slice) is
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used. In this way, the <command>bad144</command> replacement
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scheme presents <quote>perfect</quote> media to the FreeBSD filesystems.</para>
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<para>There are a number of potential pitfalls associated with the
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use of <command>bad144</command>. First of all, the slice cannot
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have more than 126 bad sectors. If your drive has a high number
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of bad sectors, you might need to divide it into multiple FreeBSD
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slices each containing less than 126 bad sectors. Stay away from
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low-level format programs that mark <emphasis>every</emphasis>
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sector of a track as bad when they find a flaw on the track. As
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you can imagine, the 126 limit is quickly reached when the
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low-level format is done this way.</para>
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<para>Second, if the slice contains the root filesystem, the slice
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should be within the 1024 cylinder BIOS limit. During the boot
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process the bad144 list is read using the BIOS and this only
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succeeds when the list is within the 1024 cylinder limit.</para>
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<note>
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<para>The restriction is not that only the root
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<emphasis>filesystem</emphasis> must be within the 1024 cylinder
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limit, but rather the entire <emphasis>slice</emphasis> that
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contains the root filesystem.</para>
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</note>
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</sect3>
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<sect3>
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<title>Kernel configuration</title>
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<para>ESDI disks are handled by the same <literal>wd</literal>driver
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as IDE and ST412 MFM disks. The <literal>wd</literal> driver
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should work for all WD1003 compatible interfaces.</para>
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<para>Most hardware is jumperable for one of two different I/O
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address ranges and IRQ lines. This allows you to have two wd
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type controllers in one system.</para>
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<para>When your hardware allows non-standard strappings, you can use
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these with FreeBSD as long as you enter the correct info into the
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kernel config file. An example from the kernel config file (they
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live in <filename>/sys/i386/conf</filename> BTW).</para>
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<programlisting># First WD compatible controller
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controller wdc0 at isa? port "IO_WD1" bio irq 14 vector wdintr
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disk wd0 at wdc0 drive 0
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disk wd1 at wdc0 drive 1
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# Second WD compatible controller
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controller wdc1 at isa? port "IO_WD2" bio irq 15 vector wdintr
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disk wd2 at wdc1 drive 0
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disk wd3 at wdc1 drive 1</programlisting>
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</sect3>
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</sect2>
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<sect2>
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<title>Particulars on ESDI hardware</title>
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<sect3>
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<title>Adaptec 2320 controllers</title>
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<para>I successfully installed FreeBSD onto a ESDI disk controlled
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by a ACB-2320. No other operating system was present on the
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disk.</para>
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<para>To do so I low level formatted the disk using
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<command>NEFMT.EXE</command> (<command>ftp</command>able from
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<hostid role="fqdn">www.adaptec.com</hostid>) and answered NO to
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the question whether the disk should be formatted with a spare
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sector on each track. The BIOS on the ACD-2320 was disabled. I
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used the <literal>free configurable</literal> option in the system
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BIOS to allow the BIOS to boot it.</para>
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<para>Before using <command>NEFMT.EXE</command> I tried to format
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the disk using the ACB-2320 BIOS built-in formatter. This proved
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to be a show stopper, because it did not give me an option to
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disable spare sectoring. With spare sectoring enabled the FreeBSD
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installation process broke down on the <command>bad144</command>
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run.</para>
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<para>Please check carefully which
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ACB-232<replaceable>xy</replaceable> variant you have. The
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<replaceable>x</replaceable> is either <literal>0</literal> or
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<literal>2</literal>, indicating a controller without or with a
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floppy controller on board.</para>
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<para>The <literal>y</literal> is more interesting. It can either
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be a blank, a <literal>A-8</literal> or a <literal>D</literal>. A
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blank indicates a plain 10 Mbits/second controller. An
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<literal>A-8</literal> indicates a 15 Mbits/second controller
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capable of handling 52 sectors/track. A <literal>D</literal>
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means a 15 Mbits/second controller that can also handle drives
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with > 36 sectors/track (also 52?).</para>
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<para>All variations should be capable of using 1:1 interleaving.
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Use 1:1, FreeBSD is fast enough to handle it.</para>
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</sect3>
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<sect3>
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<title>Western Digital WD1007 controllers</title>
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<para>I successfully installed FreeBSD onto a ESDI disk controlled
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by a WD1007 controller. To be precise, it was a WD1007-WA2.
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Other variations of the WD1007 do exist.</para>
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<para>To get it to work, I had to disable the sector translation and
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the WD1007's onboard BIOS. This implied I could not use the
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low-level formatter built into this BIOS. Instead, I grabbed
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<command>WDFMT.EXE</command> from <hostid
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role="fqdn">www.wdc.com</hostid> Running this formatted my drive
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just fine.</para>
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</sect3>
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<sect3>
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<title>Ultrastor U14F controllers</title>
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<para>According to multiple reports from the net, Ultrastor ESDI
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boards work OK with FreeBSD. I lack any further info on
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particular settings.</para>
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</sect3>
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</sect2>
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<sect2 id="esdi-further-reading">
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<title>Further reading</title>
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<para>If you intend to do some serious ESDI hacking, you might want to
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have the official standard at hand:</para>
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<para>The latest ANSI X3T10 committee document is: Enhanced Small
|
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Device Interface (ESDI) [X3.170-1990/X3.170a-1991] [X3T10/792D
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Rev 11]</para>
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<para>On Usenet the newsgroup <ulink
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url="news:comp.periphs">comp.periphs</ulink> is a noteworthy place
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to look for more info.</para>
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<para>The World Wide Web (WWW) also proves to be a very handy info
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source: For info on Adaptec ESDI controllers see <ulink
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url="http://www.adaptec.com/"></ulink>. For
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info on Western Digital controllers see
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<ulink url="http://www.wdc.com/"></ulink>.</para>
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</sect2>
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<sect2>
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<title>Thanks to...</title>
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<para>Andrew Gordon for sending me an Adaptec 2320 controller and ESDI
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disk for testing.</para>
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</sect2>
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</sect1>
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<sect1 id="scsi">
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<title>What is SCSI?</title>
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|
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<para><emphasis>Copyright © 1995, &a.wilko;. July 6,
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1996.</emphasis></para>
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|
|
<para>SCSI is an acronym for Small Computer Systems Interface. It is an
|
|
ANSI standard that has become one of the leading I/O buses in the
|
|
computer industry. The foundation of the SCSI standard was laid by
|
|
Shugart Associates (the same guys that gave the world the first mini
|
|
floppy disks) when they introduced the SASI bus (Shugart Associates
|
|
Standard Interface).</para>
|
|
|
|
<para>After some time an industry effort was started to come to a more
|
|
strict standard allowing devices from different vendors to work
|
|
together. This effort was recognized in the ANSI SCSI-1 standard.
|
|
The SCSI-1 standard (approximately 1985) is rapidly becoming obsolete. The
|
|
current standard is SCSI-2 (see <link
|
|
linkend="scsi-further-reading">Further reading</link>), with SCSI-3
|
|
on the drawing boards.</para>
|
|
|
|
<para>In addition to a physical interconnection standard, SCSI defines a
|
|
logical (command set) standard to which disk devices must adhere.
|
|
This standard is called the Common Command Set (CCS) and was developed
|
|
more or less in parallel with ANSI SCSI-1. SCSI-2 includes the
|
|
(revised) CCS as part of the standard itself. The commands are
|
|
dependent on the type of device at hand. It does not make much sense
|
|
of course to define a Write command for a scanner.</para>
|
|
|
|
<para>The SCSI bus is a parallel bus, which comes in a number of
|
|
variants. The oldest and most used is an 8 bit wide bus, with
|
|
single-ended signals, carried on 50 wires. (If you do not know what
|
|
single-ended means, do not worry, that is what this document is all
|
|
about.) Modern designs also use 16 bit wide buses, with differential
|
|
signals. This allows transfer speeds of 20Mbytes/second, on cables
|
|
lengths of up to 25 meters. SCSI-2 allows a maximum bus width of 32
|
|
bits, using an additional cable. Quickly emerging are Ultra SCSI (also
|
|
called Fast-20) and Ultra2 (also called Fast-40). Fast-20 is 20
|
|
million transfers per second (20 Mbytes/sec on a 8 bit bus), Fast-40
|
|
is 40 million transfers per second (40 Mbytes/sec on a 8 bit bus).
|
|
Most hard drives sold today are single-ended Ultra SCSI (8 or 16
|
|
bits).</para>
|
|
|
|
<para>Of course the SCSI bus not only has data lines, but also a number
|
|
of control signals. A very elaborate protocol is part of the standard
|
|
to allow multiple devices to share the bus in an efficient manner. In
|
|
SCSI-2, the data is always checked using a separate parity line. In
|
|
pre-SCSI-2 designs parity was optional.</para>
|
|
|
|
<para>In SCSI-3 even faster bus types are introduced, along with a
|
|
serial SCSI busses that reduces the cabling overhead and allows a
|
|
higher maximum bus length. You might see names like SSA and
|
|
fibre channel in this context. None of the serial buses are currently
|
|
in widespread use (especially not in the typical FreeBSD environment).
|
|
For this reason the serial bus types are not discussed any
|
|
further.</para>
|
|
|
|
<para>As you could have guessed from the description above, SCSI devices
|
|
are intelligent. They have to be to adhere to the SCSI standard
|
|
(which is over 2 inches thick BTW). So, for a hard disk drive for
|
|
instance you do not specify a head/cylinder/sector to address a
|
|
particular block, but simply the number of the block you want.
|
|
Elaborate caching schemes, automatic bad block replacement etc are all
|
|
made possible by this <quote>intelligent device</quote> approach.</para>
|
|
|
|
<para>On a SCSI bus, each possible pair of devices can communicate.
|
|
Whether their function allows this is another matter, but the standard
|
|
does not restrict it. To avoid signal contention, the 2 devices have
|
|
to arbitrate for the bus before using it.</para>
|
|
|
|
<para>The philosophy of SCSI is to have a standard that allows
|
|
older-standard devices to work with newer-standard ones. So, an old
|
|
SCSI-1 device should normally work on a SCSI-2 bus. I say Normally,
|
|
because it is not absolutely sure that the implementation of an old
|
|
device follows the (old) standard closely enough to be acceptable on a
|
|
new bus. Modern devices are usually more well-behaved, because the
|
|
standardization has become more strict and is better adhered to by the
|
|
device manufacturers.</para>
|
|
|
|
<para>Generally speaking, the chances of getting a working set of
|
|
devices on a single bus is better when all the devices are SCSI-2 or
|
|
newer. This implies that you do not have to dump all your old stuff
|
|
when you get that shiny 80GB disk: I own a system on which a pre-SCSI-1
|
|
disk, a SCSI-2 QIC tape unit, a SCSI-1 helical scan tape unit and 2
|
|
SCSI-1 disks work together quite happily. From a performance
|
|
standpoint you might want to separate your older and newer (=faster)
|
|
devices however. This is especially advantageous if you have an
|
|
Ultra160 host adapter where you should separate your U160 devices
|
|
from the Fast and Wide SCSI-2 devices.</para>
|
|
|
|
<sect2>
|
|
<title>Components of SCSI</title>
|
|
|
|
<para>As said before, SCSI devices are smart. The idea is to put the
|
|
knowledge about intimate hardware details onto the SCSI device
|
|
itself. In this way, the host system does not have to worry about
|
|
things like how many heads a hard disks has, or how many tracks
|
|
there are on a specific tape device. If you are curious, the
|
|
standard specifies commands with which you can query your devices on
|
|
their hardware particulars. FreeBSD uses this capability during
|
|
boot to check out what devices are connected and whether they need
|
|
any special treatment.</para>
|
|
|
|
<para>The advantage of intelligent devices is obvious: the device
|
|
drivers on the host can be made in a much more generic fashion,
|
|
there is no longer a need to change (and qualify!) drivers for every
|
|
odd new device that is introduced.</para>
|
|
|
|
<para>For cabling and connectors there is a golden rule: get good
|
|
stuff. With bus speeds going up all the time you will save yourself
|
|
a lot of grief by using good material.</para>
|
|
|
|
<para>So, gold plated connectors, shielded cabling, sturdy connector
|
|
hoods with strain reliefs etc are the way to go. Second golden rule:
|
|
do no use cables longer than necessary. I once spent 3 days hunting
|
|
down a problem with a flaky machine only to discover that shortening
|
|
the SCSI bus by 1 meter solved the problem. And the original bus
|
|
length was well within the SCSI specification.</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>SCSI bus types</title>
|
|
|
|
<para>From an electrical point of view, there are two incompatible bus
|
|
types: single-ended and differential. This means that there are two
|
|
different main groups of SCSI devices and controllers, which cannot
|
|
be mixed on the same bus. It is possible however to use special
|
|
converter hardware to transform a single-ended bus into a
|
|
differential one (and vice versa). The differences between the bus
|
|
types are explained in the next sections.</para>
|
|
|
|
<para>In lots of SCSI related documentation there is a sort of jargon
|
|
in use to abbreviate the different bus types. A small list:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>FWD: Fast Wide Differential</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>FND: Fast Narrow Differential</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>SE: Single Ended</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>FN: Fast Narrow</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>etc.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
|
|
<para>With a minor amount of imagination one can usually imagine what
|
|
is meant.</para>
|
|
|
|
<para>Wide is a bit ambiguous, it can indicate 16 or 32 bit buses. As
|
|
far as I know, the 32 bit variant is not (yet) in use, so wide
|
|
normally means 16 bit.</para>
|
|
|
|
<para>Fast means that the timing on the bus is somewhat different, so
|
|
that on a narrow (8 bit) bus 10 Mbytes/sec are possible instead of 5
|
|
Mbytes/sec for <quote>slow</quote> SCSI. As discussed before, bus speeds of 20
|
|
and 40 million transfers/second are also emerging (Fast-20 == Ultra
|
|
SCSI and Fast-40 == Ultra2 SCSI).</para>
|
|
|
|
<note>
|
|
<para>The data lines > 8 are only used for data transfers and
|
|
device addressing. The transfers of commands and status messages
|
|
etc are only performed on the lowest 8 data lines. The standard
|
|
allows narrow devices to operate on a wide bus. The usable bus
|
|
width is negotiated between the devices. You have to watch your
|
|
device addressing closely when mixing wide and narrow.</para>
|
|
</note>
|
|
|
|
<sect3>
|
|
<title>Single ended buses</title>
|
|
|
|
<para>A single-ended SCSI bus uses signals that are either 5 Volts
|
|
or 0 Volts (indeed, TTL levels) and are relative to a COMMON
|
|
ground reference. A singled ended 8 bit SCSI bus has
|
|
approximately 25 ground lines, who are all tied to a single <quote>rail</quote>
|
|
on all devices. A standard single ended bus has a maximum length
|
|
of 6 meters. If the same bus is used with fast-SCSI devices, the
|
|
maximum length allowed drops to 3 meters. Fast-SCSI means that
|
|
instead of 5Mbytes/sec the bus allows 10Mbytes/sec
|
|
transfers.</para>
|
|
|
|
<para>Fast-20 (Ultra SCSI) and Fast-40 allow for 20 and 40 million
|
|
transfers/second respectively. So, F20 is 20 Mbytes/second on a 8
|
|
bit bus, 40 Mbytes/second on a 16 bit bus etc. For F20 the max
|
|
bus length is 1.5 meters, for F40 it becomes 0.75 meters. Be
|
|
aware that F20 is pushing the limits quite a bit, so you will
|
|
quickly find out if your SCSI bus is electrically sound.</para>
|
|
|
|
<note>
|
|
<para>If some devices on your bus use <quote>fast</quote> to communicate your
|
|
bus must adhere to the length restrictions for fast
|
|
buses!</para>
|
|
</note>
|
|
|
|
<para>It is obvious that with the newer fast-SCSI devices the bus
|
|
length can become a real bottleneck. This is why the differential
|
|
SCSI bus was introduced in the SCSI-2 standard.</para>
|
|
|
|
<para>For connector pinning and connector types please refer to the
|
|
SCSI-2 standard (see <link linkend="scsi-further-reading">Further
|
|
reading</link>) itself, connectors etc are listed there in
|
|
painstaking detail.</para>
|
|
|
|
<para>Beware of devices using non-standard cabling. For instance
|
|
Apple uses a 25pin D-type connecter (like the one on serial ports
|
|
and parallel printers). Considering that the official SCSI bus
|
|
needs 50 pins you can imagine the use of this connector needs some
|
|
<quote>creative cabling</quote>. The reduction of the number of ground wires
|
|
they used is a bad idea, you better stick to 50 pins cabling in
|
|
accordance with the SCSI standard. For Fast-20 and 40 do not even
|
|
think about buses like this.</para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>Differential buses</title>
|
|
|
|
<para>A differential SCSI bus has a maximum length of 25 meters.
|
|
Quite a difference from the 3 meters for a single-ended fast-SCSI
|
|
bus. The idea behind differential signals is that each bus signal
|
|
has its own return wire. So, each signal is carried on a
|
|
(preferably twisted) pair of wires. The voltage difference
|
|
between these two wires determines whether the signal is asserted
|
|
or de-asserted. To a certain extent the voltage difference
|
|
between ground and the signal wire pair is not relevant (do not
|
|
try 10 kVolts though).</para>
|
|
|
|
<para>It is beyond the scope of this document to explain why this
|
|
differential idea is so much better. Just accept that
|
|
electrically seen the use of differential signals gives a much
|
|
better noise margin. You will normally find differential buses in
|
|
use for inter-cabinet connections. Because of the lower cost
|
|
single ended is mostly used for shorter buses like inside
|
|
cabinets.</para>
|
|
|
|
<para>There is nothing that stops you from using differential stuff
|
|
with FreeBSD, as long as you use a controller that has device
|
|
driver support in FreeBSD. As an example, Adaptec marketed the
|
|
AHA1740 as a single ended board, whereas the AHA1744 was
|
|
differential. The software interface to the host is identical for
|
|
both.</para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>Terminators</title>
|
|
|
|
<para>Terminators in SCSI terminology are resistor networks that are
|
|
used to get a correct impedance matching. Impedance matching is
|
|
important to get clean signals on the bus, without reflections or
|
|
ringing. If you once made a long distance telephone call on a bad
|
|
line you probably know what reflections are. With 20Mbytes/sec
|
|
traveling over your SCSI bus, you do not want signals echoing
|
|
back.</para>
|
|
|
|
<para>Terminators come in various incarnations, with more or less
|
|
sophisticated designs. Of course, there are internal and external
|
|
variants. Many SCSI devices come with a number of sockets in
|
|
which a number of resistor networks can (must be!) installed. If
|
|
you remove terminators from a device, carefully store them. You
|
|
will need them when you ever decide to reconfigure your SCSI bus.
|
|
There is enough variation in even these simple tiny things to make
|
|
finding the exact replacement a frustrating business. There are
|
|
also SCSI devices that have a single jumper to enable or disable a
|
|
built-in terminator. There are special terminators you can stick
|
|
onto a flat cable bus. Others look like external connectors, or a
|
|
connector hood without a cable. So, lots of choice as you can
|
|
see.</para>
|
|
|
|
<para>There is much debate going on if and when you should switch
|
|
from simple resistor (passive) terminators to active terminators.
|
|
Active terminators contain slightly more elaborate circuit to give
|
|
cleaner bus signals. The general consensus seems to be that the
|
|
usefulness of active termination increases when you have long
|
|
buses and/or fast devices. If you ever have problems with your
|
|
SCSI buses you might consider trying an active terminator. Try to
|
|
borrow one first, they reputedly are quite expensive.</para>
|
|
|
|
<para>Please keep in mind that terminators for differential and
|
|
single-ended buses are not identical. You should <emphasis>not
|
|
mix</emphasis> the two variants.</para>
|
|
|
|
<para>OK, and now where should you install your terminators? This is
|
|
by far the most misunderstood part of SCSI. And it is by far the
|
|
simplest. The rule is: <emphasis>every single line on the SCSI
|
|
bus has 2 (two) terminators, one at each end of the
|
|
bus.</emphasis> So, two and not one or three or whatever. Do
|
|
yourself a favor and stick to this rule. It will save you endless
|
|
grief, because wrong termination has the potential to introduce
|
|
highly mysterious bugs. (Note the <quote>potential</quote> here;
|
|
the nastiest part is that it may or may not work.)</para>
|
|
|
|
<para>A common pitfall is to have an internal (flat) cable in a
|
|
machine and also an external cable attached to the controller. It
|
|
seems almost everybody forgets to remove the terminators from the
|
|
controller. The terminator must now be on the last external
|
|
device, and not on the controller! In general, every
|
|
reconfiguration of a SCSI bus must pay attention to this.</para>
|
|
|
|
<note>
|
|
<para>Termination is to be done on a per-line basis. This means
|
|
if you have both narrow and wide buses connected to the same
|
|
host adapter, you need to enable termination on the higher 8
|
|
bits of the bus on the adapter (as well as the last devices on
|
|
each bus, of course).</para>
|
|
</note>
|
|
|
|
<para>What I did myself is remove all terminators from my SCSI
|
|
devices and controllers. I own a couple of external terminators,
|
|
for both the Centronics-type external cabling and for the internal
|
|
flat cable connectors. This makes reconfiguration much
|
|
easier.</para>
|
|
|
|
<para>On modern devices, sometimes integrated terminators are used.
|
|
These things are special purpose integrated circuits that can be
|
|
enabled or disabled with a control pin. It is not necessary to
|
|
physically remove them from a device. You may find them on newer
|
|
host adapters, sometimes they are software configurable, using
|
|
some sort of setup tool. Some will even auto-detect the cables
|
|
attached to the connectors and automatically set up the
|
|
termination as necessary. At any rate, consult your
|
|
documentation!</para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>Terminator power</title>
|
|
|
|
<para>The terminators discussed in the previous chapter need power
|
|
to operate properly. On the SCSI bus, a line is dedicated to this
|
|
purpose. So, simple huh?</para>
|
|
|
|
<para>Not so. Each device can provide its own terminator power to
|
|
the terminator sockets it has on-device. But if you have external
|
|
terminators, or when the device supplying the terminator power to
|
|
the SCSI bus line is switched off you are in trouble.</para>
|
|
|
|
<para>The idea is that initiators (these are devices that initiate
|
|
actions on the bus, a discussion follows) must supply terminator
|
|
power. All SCSI devices are allowed (but not required) to supply
|
|
terminator power.</para>
|
|
|
|
<para>To allow for un-powered devices on a bus, the terminator power
|
|
must be supplied to the bus via a diode. This prevents the
|
|
backflow of current to un-powered devices.</para>
|
|
|
|
<para>To prevent all kinds of nastiness, the terminator power is
|
|
usually fused. As you can imagine, fuses might blow. This can,
|
|
but does not have to, lead to a non functional bus. If multiple
|
|
devices supply terminator power, a single blown fuse will not put
|
|
you out of business. A single supplier with a blown fuse
|
|
certainly will. Clever external terminators sometimes have a LED
|
|
indication that shows whether terminator power is present.</para>
|
|
|
|
<para>In newer designs auto-restoring fuses that <quote>reset</quote> themselves
|
|
after some time are sometimes used.</para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>Device addressing</title>
|
|
|
|
<para>Because the SCSI bus is, ehh, a bus there must be a way to
|
|
distinguish or address the different devices connected to
|
|
it.</para>
|
|
|
|
<para>This is done by means of the SCSI or target ID. Each device
|
|
has a unique target ID. You can select the ID to which a device
|
|
must respond using a set of jumpers, or a dip switch, or something
|
|
similar. Some SCSI host adapters let you change the target ID
|
|
from the boot menu. (Yet some others will not let you change the
|
|
ID from 7.) Consult the documentation of your device for more
|
|
information.</para>
|
|
|
|
<para>Beware of multiple devices configured to use the same ID.
|
|
Chaos normally reigns in this case. A pitfall is that one of the
|
|
devices sharing the same ID sometimes even manages to answer to
|
|
I/O requests!</para>
|
|
|
|
<para>For an 8 bit bus, a maximum of 8 targets is possible. The
|
|
maximum is 8 because the selection is done bitwise using the 8
|
|
data lines on the bus. For wide buses this increases to the
|
|
number of data lines (usually 16).</para>
|
|
|
|
<note>
|
|
<para>A narrow SCSI device can not communicate with a SCSI device
|
|
with a target ID larger than 7. This means it is generally not
|
|
a good idea to move your SCSI host adapter's target ID to
|
|
something higher than 7 (or your CDROM will stop
|
|
working).</para>
|
|
</note>
|
|
|
|
<para>The higher the SCSI target ID, the higher the priority the
|
|
devices has. When it comes to arbitration between devices that
|
|
want to use the bus at the same time, the device that has the
|
|
highest SCSI ID will win. This also means that the SCSI host
|
|
adapter usually uses target ID 7. Note however that the lower 8
|
|
IDs have higher priorities than the higher 8 IDs on a wide-SCSI
|
|
bus. Thus, the order of target IDs is: [7 6 .. 1 0 15 14 .. 9 8]
|
|
on a wide-SCSI system. (If you are wondering why the lower 8
|
|
have higher priority, read the previous paragraph for a
|
|
hint.)</para>
|
|
|
|
<para>For a further subdivision, the standard allows for Logical
|
|
Units or LUNs for short. A single target ID may have multiple
|
|
LUNs. For example, a tape device including a tape changer may
|
|
have LUN 0 for the tape device itself, and LUN 1 for the tape
|
|
changer. In this way, the host system can address each of the
|
|
functional units of the tape changer as desired.</para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>Bus layout</title>
|
|
|
|
<para>SCSI buses are linear. So, not shaped like Y-junctions, star
|
|
topologies, rings, cobwebs or whatever else people might want to
|
|
invent. One of the most common mistakes is for people with
|
|
wide-SCSI host adapters to connect devices on all three connecters
|
|
(external connector, internal wide connector, internal narrow
|
|
connector). Do not do that. It may appear to work if you are
|
|
really lucky, but I can almost guarantee that your system will
|
|
stop functioning at the most unfortunate moment (this is also
|
|
known as <quote>Murphy's law</quote>).</para>
|
|
|
|
<para>You might notice that the terminator issue discussed earlier
|
|
becomes rather hairy if your bus is not linear. Also, if you have
|
|
more connectors than devices on your internal SCSI cable, make
|
|
sure you attach devices on connectors on both ends instead of
|
|
using the connectors in the middle and let one or both ends
|
|
dangle. This will screw up the termination of the bus.</para>
|
|
|
|
<para>The electrical characteristics, its noise margins and
|
|
ultimately the reliability of it all are tightly related to linear
|
|
bus rule.</para>
|
|
|
|
<para><emphasis>Stick to the linear bus rule!</emphasis></para>
|
|
</sect3>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Using SCSI with FreeBSD</title>
|
|
|
|
<sect3>
|
|
<title>About translations, BIOSes and magic...</title>
|
|
|
|
<para>As stated before, you should first make sure that you have a
|
|
electrically sound bus.</para>
|
|
|
|
<para>When you want to use a SCSI disk on your PC as boot disk, you
|
|
must aware of some quirks related to PC BIOSes. The PC BIOS in
|
|
its first incarnation used a low level physical interface to the
|
|
hard disk. So, you had to tell the BIOS (using a setup tool or a
|
|
BIOS built-in setup) how your disk physically looked like. This
|
|
involved stating number of heads, number of cylinders, number of
|
|
sectors per track, obscure things like precompensation and reduced
|
|
write current cylinder etc.</para>
|
|
|
|
<para>One might be inclined to think that since SCSI disks are smart
|
|
you can forget about this. Alas, the arcane setup issue is still
|
|
present today. The system BIOS needs to know how to access your
|
|
SCSI disk with the head/cyl/sector method in order to load the
|
|
FreeBSD kernel during boot.</para>
|
|
|
|
<para>The SCSI host adapter or SCSI controller you have put in your
|
|
AT/EISA/PCI/whatever bus to connect your disk therefore has its
|
|
own on-board BIOS. During system startup, the SCSI BIOS takes
|
|
over the hard disk interface routines from the system BIOS. To
|
|
fool the system BIOS, the system setup is normally set to No hard
|
|
disk present. Obvious, is it not?</para>
|
|
|
|
<para>The SCSI BIOS itself presents to the system a so called
|
|
<emphasis>translated</emphasis> drive. This means that a fake
|
|
drive table is constructed that allows the PC to boot the drive.
|
|
This translation is often (but not always) done using a pseudo
|
|
drive with 64 heads and 32 sectors per track. By varying the
|
|
number of cylinders, the SCSI BIOS adapts to the actual drive
|
|
size. It is useful to note that 32 * 64 / 2 = the size of your
|
|
drive in megabytes. The division by 2 is to get from disk blocks
|
|
that are normally 512 bytes in size to Kbytes.</para>
|
|
|
|
<para>Right. All is well now?! No, it is not. The system BIOS has
|
|
another quirk you might run into. The number of cylinders of a
|
|
bootable hard disk cannot be greater than 1024. Using the
|
|
translation above, this is a show-stopper for disks greater than 1
|
|
GB. With disk capacities going up all the time this is causing
|
|
problems.</para>
|
|
|
|
<para>Fortunately, the solution is simple: just use another
|
|
translation, e.g. with 128 heads instead of 32. In most cases new
|
|
SCSI BIOS versions are available to upgrade older SCSI host
|
|
adapters. Some newer adapters have an option, in the form of a
|
|
jumper or software setup selection, to switch the translation the
|
|
SCSI BIOS uses.</para>
|
|
|
|
<para>It is very important that <emphasis>all</emphasis> operating
|
|
systems on the disk use the <emphasis>same translation</emphasis>
|
|
to get the right idea about where to find the relevant partitions.
|
|
So, when installing FreeBSD you must answer any questions about
|
|
heads/cylinders etc using the translated values your host adapter
|
|
uses.</para>
|
|
|
|
<para>Failing to observe the translation issue might lead to
|
|
un-bootable systems or operating systems overwriting each others
|
|
partitions. Using fdisk you should be able to see all
|
|
partitions.</para>
|
|
|
|
<para>You might have heard some talk of <quote>lying</quote> devices?
|
|
Older FreeBSD kernels used to report the geometry of SCSI disks
|
|
when booting. An example from one of my systems:</para>
|
|
|
|
<screen>aha0 targ 0 lun 0: <MICROP 1588-15MB1057404HSP4>
|
|
da0: 636MB (1303250 total sec), 1632 cyl, 15 head, 53 sec, bytes/sec 512</screen>
|
|
|
|
<para>Newer kernels usually do not report this information.
|
|
e.g.</para>
|
|
|
|
<screen>(bt0:0:0): "SEAGATE ST41651 7574" type 0 fixed SCSI 2
|
|
da0(bt0:0:0): Direct-Access 1350MB (2766300 512 byte sectors)</screen>
|
|
|
|
<para>Why has this changed?</para>
|
|
|
|
<para>This info is retrieved from the SCSI disk itself. Newer disks
|
|
often use a technique called zone bit recording. The idea is that
|
|
on the outer cylinders of the drive there is more space so more
|
|
sectors per track can be put on them. This results in disks that
|
|
have more tracks on outer cylinders than on the inner cylinders
|
|
and, last but not least, have more capacity. You can imagine that
|
|
the value reported by the drive when inquiring about the geometry
|
|
now becomes suspect at best, and nearly always misleading. When
|
|
asked for a geometry, it is nearly always better to supply the
|
|
geometry used by the BIOS, or <emphasis>if the BIOS is never going
|
|
to know about this disk</emphasis>, (e.g. it is not a booting
|
|
disk) to supply a fictitious geometry that is convenient.</para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>SCSI subsystem design</title>
|
|
|
|
<para>FreeBSD uses a layered SCSI subsystem. For each different
|
|
controller card a device driver is written. This driver knows all
|
|
the intimate details about the hardware it controls. The driver
|
|
has a interface to the upper layers of the SCSI subsystem through
|
|
which it receives its commands and reports back any status.</para>
|
|
|
|
<para>On top of the card drivers there are a number of more generic
|
|
drivers for a class of devices. More specific: a driver for tape
|
|
devices (abbreviation: sa, for serial access),
|
|
magnetic disks (da, for direct access), CDROMs (cd) etc.
|
|
In case you are wondering where you can find this stuff, it all
|
|
lives in <filename>/sys/cam/scsi</filename>. See the man pages in
|
|
section 4 for more details.</para>
|
|
|
|
<para>The multi level design allows a decoupling of low-level bit
|
|
banging and more high level stuff. Adding support for another
|
|
piece of hardware is a much more manageable problem.</para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>Kernel configuration</title>
|
|
|
|
<para>Dependent on your hardware, the kernel configuration file must
|
|
contain one or more lines describing your host adapter(s). This
|
|
includes I/O addresses, interrupts etc. Consult the manual page for
|
|
your adapter driver to get more info. Apart from that, check out
|
|
<filename>/sys/i386/conf/LINT</filename> for an overview of a
|
|
kernel config file. <filename>LINT</filename> contains every
|
|
possible option you can dream of. It does
|
|
<emphasis>not</emphasis> imply <filename>LINT</filename> will
|
|
actually get you to a working kernel at all.</para>
|
|
|
|
<para>Although it is probably stating the obvious: the kernel config
|
|
file should reflect your actual hardware setup. So, interrupts,
|
|
I/O addresses etc must match the kernel config file. During
|
|
system boot messages will be displayed to indicate whether the
|
|
configured hardware was actually found.</para>
|
|
|
|
<note>
|
|
<para>Note that most of the EISA/PCI drivers (namely
|
|
<devicename>ahb</devicename>, <devicename>ahc</devicename>,
|
|
<devicename>ncr</devicename> and <devicename>amd</devicename>
|
|
will automatically obtain the correct parameters from the host
|
|
adapters themselves at boot time; thus, you just need to write,
|
|
for instance, <literal>controller ahc0</literal>.</para>
|
|
</note>
|
|
|
|
<para>An example loosely based on the FreeBSD 2.2.5-Release kernel
|
|
config file <filename>LINT</filename> with some added comments
|
|
(between []):</para>
|
|
|
|
<programlisting># SCSI host adapters: `aha', `ahb', `aic', `bt', `nca'
|
|
#
|
|
# aha: Adaptec 154x
|
|
# ahb: Adaptec 174x
|
|
# ahc: Adaptec 274x/284x/294x
|
|
# aic: Adaptec 152x and sound cards using the Adaptec AIC-6360 (slow!)
|
|
# amd: AMD 53c974 based SCSI cards (e.g., Tekram DC-390 and 390T)
|
|
# bt: Most Buslogic controllers
|
|
# nca: ProAudioSpectrum cards using the NCR 5380 or Trantor T130
|
|
# ncr: NCR/Symbios 53c810/815/825/875 etc based SCSI cards
|
|
# uha: UltraStore 14F and 34F
|
|
# sea: Seagate ST01/02 8 bit controller (slow!)
|
|
# wds: Western Digital WD7000 controller (no scatter/gather!).
|
|
#
|
|
|
|
[For an Adaptec AHA274x/284x/294x/394x etc controller]
|
|
controller ahc0
|
|
|
|
[For an NCR/Symbios 53c875 based controller]
|
|
controller ncr0
|
|
|
|
[For an Ultrastor adapter]
|
|
controller uha0 at isa? port "IO_UHA0" bio irq ? drq 5 vector uhaintr
|
|
|
|
# Map SCSI buses to specific SCSI adapters
|
|
controller scbus0 at ahc0
|
|
controller scbus2 at ncr0
|
|
controller scbus1 at uha0
|
|
|
|
# The actual SCSI devices
|
|
disk da0 at scbus0 target 0 unit 0 [SCSI disk 0 is at scbus 0, LUN 0]
|
|
disk da1 at scbus0 target 1 [implicit LUN 0 if omitted]
|
|
disk da2 at scbus1 target 3 [SCSI disk on the uha0]
|
|
disk da3 at scbus2 target 4 [SCSI disk on the ncr0]
|
|
tape sa1 at scbus0 target 6 [SCSI tape at target 6]
|
|
device cd0 at scbus? [the first ever CDROM found, no wiring]</programlisting>
|
|
|
|
<para>The example above tells the kernel to look for a ahc (Adaptec
|
|
274x) controller, then for an NCR/Symbios board, and so on. The
|
|
lines following the controller specifications tell the kernel to
|
|
configure specific devices but <emphasis>only</emphasis> attach
|
|
them when they match the target ID and LUN specified on the
|
|
corresponding bus.</para>
|
|
|
|
<para>Wired down devices get <quote>first shot</quote> at the unit
|
|
numbers so the first non <quote>wired down</quote> device, is
|
|
allocated the unit number one greater than the highest
|
|
<quote>wired down</quote> unit number for that kind of device. So,
|
|
if you had a SCSI tape at target ID 2 it would be configured as
|
|
sa2, as the tape at target ID 6 is wired down to unit number
|
|
1.</para>
|
|
|
|
<note>
|
|
<para>Wired down devices need not be found to get their unit
|
|
number. The unit number for a wired down device is reserved for
|
|
that device, even if it is turned off at boot time. This allows
|
|
the device to be turned on and brought on-line at a later time,
|
|
without rebooting. Notice that a device's unit number has
|
|
<emphasis>no</emphasis> relationship with its target ID on the
|
|
SCSI bus.</para>
|
|
</note>
|
|
|
|
<para>Below is another example of a kernel config file as used by
|
|
FreeBSD version < 2.0.5. The difference with the first example
|
|
is that devices are not <quote>wired down</quote>. <quote>Wired
|
|
down</quote> means that you specify which SCSI target belongs to
|
|
which device.</para>
|
|
|
|
<para>A kernel built to the config file below will attach the first
|
|
SCSI disk it finds to da0, the second disk to da1 etc. If you ever
|
|
removed or added a disk, all other devices of the same type (disk
|
|
in this case) would <quote>move around</quote>. This implies you have to
|
|
change <filename>/etc/fstab</filename> each time.</para>
|
|
|
|
<para>Although the old style still works, you are
|
|
<emphasis>strongly</emphasis> recommended to use this new feature.
|
|
It will save you a lot of grief whenever you shift your hardware
|
|
around on the SCSI buses. So, when you re-use your old trusty
|
|
config file after upgrading from a pre-FreeBSD2.0.5.R system check
|
|
this out.</para>
|
|
|
|
<programlisting>[driver for Adaptec 174x]
|
|
controller ahb0 at isa? bio irq 11 vector ahbintr
|
|
|
|
[for Adaptec 154x]
|
|
controller aha0 at isa? port "IO_AHA0" bio irq 11 drq 5 vector ahaintr
|
|
|
|
[for Seagate ST01/02]
|
|
controller sea0 at isa? bio irq 5 iomem 0xc8000 iosiz 0x2000 vector seaintr
|
|
|
|
controller scbus0
|
|
|
|
device da0 [support for 4 SCSI harddisks, da0 up da3]
|
|
device sa0 [support for 2 SCSI tapes]
|
|
|
|
[for the CDROM]
|
|
device cd0 #Only need one of these, the code dynamically grows</programlisting>
|
|
|
|
<para>Both examples support SCSI disks. If during boot more devices
|
|
of a specific type (e.g. da disks) are found than are configured
|
|
in the booting kernel, the system will simply allocate more
|
|
devices, incrementing the unit number starting at the last number
|
|
<quote>wired down</quote>. If there are no <quote>wired
|
|
down</quote> devices then counting starts at unit 0.</para>
|
|
|
|
<para>Use <command>man 4 scsi</command> to check for the latest info
|
|
on the SCSI subsystem. For more detailed info on host adapter
|
|
drivers use e.g., <command>man 4 ahc</command> for info on the
|
|
Adaptec 294x driver.</para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>Tuning your SCSI kernel setup</title>
|
|
|
|
<para>Experience has shown that some devices are slow to respond to
|
|
INQUIRY commands after a SCSI bus reset (which happens at boot
|
|
time). An INQUIRY command is sent by the kernel on boot to see
|
|
what kind of device (disk, tape, CDROM etc.) is connected to a
|
|
specific target ID. This process is called device probing by the
|
|
way.</para>
|
|
|
|
<para>To work around the <quote>slow response</quote> problem, FreeBSD allows a
|
|
tunable delay time before the SCSI devices are probed following a
|
|
SCSI bus reset. You can set this delay time in your kernel
|
|
configuration file using a line like:</para>
|
|
|
|
<programlisting>options SCSI_DELAY=15 #Be pessimistic about Joe SCSI device</programlisting>
|
|
|
|
<para>This line sets the delay time to 15 seconds. On my own system
|
|
I had to use 3 seconds minimum to get my trusty old CDROM drive
|
|
to be recognized. Start with a high value (say 30 seconds or so)
|
|
when you have problems with device recognition. If this helps,
|
|
tune it back until it just stays working.</para>
|
|
</sect3>
|
|
|
|
<sect3 id="scsi-rogue-devices">
|
|
<title>Rogue SCSI devices</title>
|
|
|
|
<para>Although the SCSI standard tries to be complete and concise,
|
|
it is a complex standard and implementing things correctly is no
|
|
easy task. Some vendors do a better job then others.</para>
|
|
|
|
<para>This is exactly where the <quote>rogue</quote> devices come
|
|
into view. Rogues are devices that are recognized by the FreeBSD
|
|
kernel as behaving slightly (...) non-standard. Rogue devices are
|
|
reported by the kernel when booting. An example for two of my
|
|
cartridge tape units:</para>
|
|
|
|
<screen>Feb 25 21:03:34 yedi /kernel: ahb0 targ 5 lun 0: <TANDBERG TDC 3600 -06:>
|
|
Feb 25 21:03:34 yedi /kernel: sa0: Tandberg tdc3600 is a known rogue
|
|
|
|
Mar 29 21:16:37 yedi /kernel: aha0 targ 5 lun 0: <ARCHIVE VIPER 150 21247-005>
|
|
Mar 29 21:16:37 yedi /kernel: sa1: Archive Viper 150 is a known rogue </screen>
|
|
|
|
<para>For instance, there are devices that respond to all LUNs on a
|
|
certain target ID, even if they are actually only one device. It
|
|
is easy to see that the kernel might be fooled into believing that
|
|
there are 8 LUNs at that particular target ID. The confusion this
|
|
causes is left as an exercise to the reader.</para>
|
|
|
|
<para>The SCSI subsystem of FreeBSD recognizes devices with bad
|
|
habits by looking at the INQUIRY response they send when probed.
|
|
Because the INQUIRY response also includes the version number of
|
|
the device firmware, it is even possible that for different
|
|
firmware versions different workarounds are used. See e.g.
|
|
<filename>/sys/cam/scsi/scsi_sa.c</filename> and
|
|
<filename>/sys/cam/scsi/scsi_all.c</filename> for more info on how
|
|
this is done.</para>
|
|
|
|
<para>This scheme works fine, but keep in mind that it of course
|
|
only works for devices that are known to be weird. If you are the
|
|
first to connect your bogus Mumbletech SCSI CDROM you might be
|
|
the one that has to define which workaround is needed.</para>
|
|
|
|
<para>After you got your Mumbletech working, please send the
|
|
required workaround to the FreeBSD development team for inclusion
|
|
in the next release of FreeBSD. Other Mumbletech owners will be
|
|
grateful to you.</para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>Multiple LUN devices</title>
|
|
|
|
<para>In some cases you come across devices that use multiple
|
|
logical units (LUNs) on a single SCSI ID. In most cases FreeBSD
|
|
only probes devices for LUN 0. An example are so called bridge
|
|
boards that connect 2 non-SCSI hard disks to a SCSI bus (e.g. an
|
|
Emulex MD21 found in old Sun systems).</para>
|
|
|
|
<para>This means that any devices with LUNs != 0 are not normally
|
|
found during device probe on system boot. To work around this
|
|
problem you must add an appropriate entry in /sys/cam/scsi
|
|
and rebuild your kernel.</para>
|
|
|
|
<para>Look for a struct that is initialized like below:
|
|
(FIXME: which file? Do these entries still exist in this form
|
|
now that we use CAM?)</para>
|
|
|
|
<programlisting>{
|
|
T_DIRECT, T_FIXED, "MAXTOR", "XT-4170S", "B5A",
|
|
"mx1", SC_ONE_LU
|
|
}</programlisting>
|
|
|
|
<para>For your Mumbletech BRIDGE2000 that has more than one LUN, acts
|
|
as a SCSI disk and has firmware revision 123 you would add
|
|
something like:</para>
|
|
|
|
<programlisting>{
|
|
T_DIRECT, T_FIXED, "MUMBLETECH", "BRIDGE2000", "123",
|
|
"da", SC_MORE_LUS
|
|
}</programlisting>
|
|
|
|
<para>The kernel on boot scans the inquiry data it receives against
|
|
the table and acts accordingly. See the source for more
|
|
info.</para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>Tagged command queuing</title>
|
|
|
|
<para>Modern SCSI devices, particularly magnetic disks,
|
|
support what is called tagged command queuing (TCQ).</para>
|
|
|
|
<para>In a nutshell, TCQ allows the device to have multiple I/O
|
|
requests outstanding at the same time. Because the device is
|
|
intelligent, it can optimize its operations (like head
|
|
positioning) based on its own request queue. On SCSI devices
|
|
like RAID (Redundant Array of Independent Disks) arrays the TCQ
|
|
function is indispensable to take advantage of the device's
|
|
inherent parallelism.</para>
|
|
|
|
<para>Each I/O request is uniquely identified by a <quote>tag</quote>
|
|
(hence the name tagged command queuing) and this tag is used by
|
|
FreeBSD to see which I/O in the device drivers queue is reported
|
|
as complete by the device.</para>
|
|
|
|
<para>It should be noted however that TCQ requires device driver
|
|
support and that some devices implemented it <quote>not quite
|
|
right</quote> in their firmware. This problem bit me once, and it
|
|
leads to highly mysterious problems. In such cases, try to
|
|
disable TCQ.</para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>Bus-master host adapters</title>
|
|
|
|
<para>Most, but not all, SCSI host adapters are bus mastering
|
|
controllers. This means that they can do I/O on their own without
|
|
putting load onto the host CPU for data movement.</para>
|
|
|
|
<para>This is of course an advantage for a multitasking operating
|
|
system like FreeBSD. It must be noted however that there might be
|
|
some rough edges.</para>
|
|
|
|
<para>For instance an Adaptec 1542 controller can be set to use
|
|
different transfer speeds on the host bus (ISA or AT in this
|
|
case). The controller is settable to different rates because not
|
|
all motherboards can handle the higher speeds. Problems like
|
|
hang-ups, bad data etc might be the result of using a higher data
|
|
transfer rate then your motherboard can stomach.</para>
|
|
|
|
<para>The solution is of course obvious: switch to a lower data
|
|
transfer rate and try if that works better.</para>
|
|
|
|
<para>In the case of a Adaptec 1542, there is an option that can be
|
|
put into the kernel config file to allow dynamic determination of
|
|
the right, read: fastest feasible, transfer rate. This option is
|
|
disabled by default:</para>
|
|
|
|
<programlisting>options "TUNE_1542" #dynamic tune of bus DMA speed</programlisting>
|
|
|
|
<para>Check the manual pages for the host adapter that you use. Or
|
|
better still, use the ultimate documentation (read: driver
|
|
source).</para>
|
|
</sect3>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Tracking down problems</title>
|
|
|
|
<para>The following list is an attempt to give a guideline for the
|
|
most common SCSI problems and their solutions. It is by no means
|
|
complete.</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>Check for loose connectors and cables.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Check and double check the location and number of your
|
|
terminators.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Check if your bus has at least one supplier of terminator
|
|
power (especially with external terminators.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Check if no double target IDs are used.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Check if all devices to be used are powered up.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Make a minimal bus config with as little devices as
|
|
possible.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>If possible, configure your host adapter to use slow bus
|
|
speeds.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Disable tagged command queuing to make things as simple as
|
|
possible (for a NCR host adapter based system see man
|
|
ncrcontrol)</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>If you can compile a kernel, make one with the
|
|
<literal>SCSIDEBUG</literal> option, and try accessing the
|
|
device with debugging turned on for that device. If your device
|
|
does not even probe at startup, you may have to define the
|
|
address of the device that is failing, and the desired debug
|
|
level in <filename>/sys/cam/cam_debug.h</filename>. If it
|
|
probes but just does not work, you can use the
|
|
&man.camcontrol.8; command to dynamically set a debug level to
|
|
it in a running kernel (if <literal>CAMDEBUG</literal> is
|
|
defined). This will give you <emphasis>copious</emphasis>
|
|
debugging output with which to confuse the gurus. See
|
|
<command>man camcontrol</command> for more exact information. Also
|
|
look at <command>man 4 pass</command>.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</sect2>
|
|
|
|
<sect2 id="scsi-further-reading">
|
|
<title>Further reading</title>
|
|
|
|
<para>If you intend to do some serious SCSI hacking, you might want to
|
|
have the official standard at hand:</para>
|
|
|
|
<para>Approved American National Standards can be purchased from
|
|
ANSI at
|
|
|
|
<address>
|
|
<otheraddr>13th Floor</otheraddr>
|
|
<street>11 West 42nd Street</street>
|
|
<city>New York</city>
|
|
<state>NY</state> <postcode>10036</postcode>
|
|
Sales Dept: <phone>(212) 642-4900</phone>
|
|
</address>
|
|
</para>
|
|
|
|
<para>You can also buy many ANSI
|
|
standards and most committee draft documents from Global
|
|
Engineering Documents,
|
|
|
|
<address>
|
|
<street>15 Inverness Way East</street>
|
|
<city>Englewood</city>
|
|
<state>CO</state>, <postcode>80112-5704</postcode>
|
|
Phone: <phone>(800) 854-7179</phone>
|
|
Outside USA and Canada: <phone>(303) 792-2181</phone>
|
|
Fax: <fax>(303) 792- 2192</fax>
|
|
</address>
|
|
</para>
|
|
|
|
<para>Many X3T10 draft documents are available electronically on the
|
|
SCSI BBS (719-574-0424) and on the <hostid
|
|
role="fqdn">ncrinfo.ncr.com</hostid> anonymous FTP site.</para>
|
|
|
|
<para>Latest X3T10 committee documents are:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>AT Attachment (ATA or IDE) [X3.221-1994]
|
|
(<emphasis>Approved</emphasis>)</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>ATA Extensions (ATA-2) [X3T10/948D Rev 2i]</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Enhanced Small Device Interface (ESDI)
|
|
[X3.170-1990/X3.170a-1991]
|
|
(<emphasis>Approved</emphasis>)</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Small Computer System Interface — 2 (SCSI-2)
|
|
[X3.131-1994] (<emphasis>Approved</emphasis>)</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>SCSI-2 Common Access Method Transport and SCSI Interface
|
|
Module (CAM) [X3T10/792D Rev 11]</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>Other publications that might provide you with additional
|
|
information are:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para><quote>SCSI: Understanding the Small Computer System
|
|
Interface</quote>, written by NCR Corporation. Available from:
|
|
Prentice Hall, Englewood Cliffs, NJ, 07632 Phone: (201) 767-5937
|
|
ISBN 0-13-796855-8</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><quote>Basics of SCSI</quote>, a SCSI tutorial written by
|
|
Ancot Corporation Contact Ancot for availability information at:
|
|
Phone: (415) 322-5322 Fax: (415) 322-0455</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><quote>SCSI Interconnection Guide Book</quote>, an AMP
|
|
publication (dated 4/93, Catalog 65237) that lists the various
|
|
SCSI connectors and suggests cabling schemes. Available from
|
|
AMP at (800) 522-6752 or (717) 564-0100</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><quote>Fast Track to SCSI</quote>, A Product Guide written by
|
|
Fujitsu. Available from: Prentice Hall, Englewood Cliffs, NJ,
|
|
07632 Phone: (201) 767-5937 ISBN 0-13-307000-X</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><quote>The SCSI Bench Reference</quote>, <quote>The SCSI
|
|
Encyclopedia</quote>, and the <quote>SCSI Tutor</quote>, ENDL
|
|
Publications, 14426 Black Walnut Court, Saratoga CA, 95070
|
|
Phone: (408) 867-6642</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><quote>Zadian SCSI Navigator</quote> (quick ref. book) and
|
|
<quote>Discover the Power of SCSI</quote> (First book along with
|
|
a one-hour video and tutorial book), Zadian Software, Suite 214,
|
|
1210 S. Bascom Ave., San Jose, CA 92128, (408) 293-0800</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>On Usenet the newsgroups <ulink
|
|
url="news:comp.periphs.scsi">comp.periphs.scsi</ulink> and <ulink
|
|
url="news:comp.periphs">comp.periphs</ulink> are noteworthy places
|
|
to look for more info. You can also find the <ulink
|
|
url="http://scsifaq.org:9080/scsi_faq/scsifaq.html">SCSI-FAQ</ulink>
|
|
there, which is posted periodically.</para>
|
|
|
|
<para>Most major SCSI device and host adapter suppliers operate FTP
|
|
sites and/or BBS systems. They may be valuable sources of
|
|
information about the devices you own.</para>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 id="hw-storage-controllers">
|
|
<title>* Disk/tape controllers</title>
|
|
|
|
<sect2>
|
|
<title>* SCSI</title>
|
|
|
|
<para></para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>* IDE</title>
|
|
|
|
<para></para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>* Floppy</title>
|
|
|
|
<para></para>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1>
|
|
<title>Hard drives</title>
|
|
|
|
<sect2>
|
|
<title>SCSI hard drives</title>
|
|
|
|
<para><emphasis>Contributed by &a.asami;. 17 February
|
|
1998.</emphasis></para>
|
|
|
|
<para>As mentioned in the <link linkend="scsi">SCSI</link> section,
|
|
virtually all SCSI hard drives sold today are SCSI-2 compliant and
|
|
thus will work fine as long as you connect them to a supported SCSI
|
|
host adapter. Most problems people encounter are either due to
|
|
badly designed cabling (cable too long, star topology, etc.),
|
|
insufficient termination, or defective parts. Please refer to the
|
|
<link linkend="scsi">SCSI</link> section first if your SCSI hard
|
|
drive is not working. However, there are a couple of things you may
|
|
want to take into account before you purchase SCSI hard drives for
|
|
your system.</para>
|
|
|
|
<sect3>
|
|
<title>Rotational speed</title>
|
|
|
|
<para>Rotational speeds of SCSI drives sold today range from around
|
|
4,500RPM to 15,000RPM. Most of them are either 7,200RPM or
|
|
10,000RPM, with 15,000RPM becoming affordable (June 2002).
|
|
Even though the 10,000RPM drives can generally transfer
|
|
data faster, they run considerably hotter than their 7,200RPM
|
|
counterparts. A large fraction of today's disk drive malfunctions
|
|
are heat-related. If you do not have very good cooling in your PC
|
|
case, you may want to stick with 7,200RPM or slower drives.</para>
|
|
|
|
<para>Note that newer drives, with higher areal recording densities,
|
|
can deliver much more bits per rotation than older ones. Today's
|
|
top-of-line 7,200RPM drives can sustain a throughput comparable to
|
|
10,000RPM drives of one or two model generations ago. The number
|
|
to find on the spec sheet for bandwidth is <quote>internal data
|
|
(or transfer) rate</quote>. It is usually in megabits/sec so
|
|
divide it by 8 and you will get the rough approximation of how much
|
|
megabytes/sec you can get out of the drive.</para>
|
|
|
|
<para>(If you are a speed maniac and want a 15,000RPM drive for your
|
|
cute little PC, be my guest; however, those drives become
|
|
extremely hot. Do not even think about it if you do not have a fan
|
|
blowing air <emphasis>directly at</emphasis> the drive or a
|
|
properly ventilated disk enclosure.)</para>
|
|
|
|
<para>Obviously, the latest 15,000RPM drives and 10,000RPM drives can
|
|
deliver more data than the latest 7,200RPM drives, so if absolute
|
|
bandwidth is the necessity for your applications, you have little
|
|
choice but to get the faster drives. Also, if you need low
|
|
latency, faster drives are better; not only do they usually have
|
|
lower average seek times, but also the rotational delay is one
|
|
place where slow-spinning drives can never beat a faster one.
|
|
(The average rotational latency is half the time it takes to
|
|
rotate the drive once; thus, it is 2 milliseconds for 15,000RPM,
|
|
3ms for 10,000RPM
|
|
drives, 4.2ms for 7,200RPM drives and 5.6ms for 5,400RPM drives.)
|
|
Latency is seek time plus rotational delay. Make sure you
|
|
understand whether you need low latency or more accesses per
|
|
second, though; in the latter case (e.g., news servers), it may
|
|
not be optimal to purchase one big fast drive. You can achieve
|
|
similar or even better results by using the ccd (concatenated
|
|
disk) driver to create a striped disk array out of multiple slower
|
|
drives for comparable overall cost.</para>
|
|
|
|
<para>Make sure you have adequate air flow around the drive,
|
|
especially if you are going to use a fast-spinning drive. You
|
|
generally need at least 1/2” (1.25cm) of spacing above and below a
|
|
drive. Understand how the air flows through your PC case. Most
|
|
cases have the power supply suck the air out of the back. See
|
|
where the air flows in, and put the drive where it will have the
|
|
largest volume of cool air flowing around it. You may need to seal
|
|
some unwanted holes or add a new fan for effective cooling.</para>
|
|
|
|
<para>Another consideration is noise. Many 10,000 or faster drives
|
|
generate a high-pitched whine which is quite unpleasant to most
|
|
people. That, plus the extra fans often required for cooling, may
|
|
make 10,000 or faster drives unsuitable for some office and home
|
|
environments.</para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>Form factor</title>
|
|
|
|
<para>Most SCSI drives sold today are of 3.5” form factor. They
|
|
come in two different heights; 1.6” (<quote>half-height</quote>) or
|
|
1” (<quote>low-profile</quote>). The half-height drive is the same
|
|
height as a CDROM drive. However, do not forget the spacing rule
|
|
mentioned in the previous section. If you have three standard
|
|
3.5” drive bays, you will not be able to put three half-height
|
|
drives in there (without frying them, that is).</para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>Interface</title>
|
|
|
|
<para>The majority of SCSI hard drives sold today are Ultra,
|
|
Ultra-wide, or Ultra160 SCSI. As of this writing (June 2002),
|
|
the first Ultra320 host adapters and devices become available.
|
|
The maximum bandwidth of Ultra SCSI is 20MB/sec,
|
|
and Ultra-wide SCSI is 40MB/sec. Ultra160 can transfer 160MB/sec
|
|
and Ultra320 can transfer 320MB/sec. There is no difference in max
|
|
cable length between Ultra and Ultra-wide; however, the more
|
|
devices you have on the same bus, the sooner you will start having
|
|
bus integrity problems. Unless you have a well-designed disk
|
|
enclosure, it is not easy to make more than 5 or 6 Ultra SCSI
|
|
drives work on a single bus.</para>
|
|
|
|
<para>On the other hand, if you need to connect many drives, going
|
|
for Fast-wide SCSI may not be a bad idea. That will have the same
|
|
max bandwidth as Ultra (narrow) SCSI, while electronically it is
|
|
much easier to get it <quote>right</quote>. My advice would be: if
|
|
you want to connect many disks, get wide or Ultra160 SCSI drives;
|
|
they usually
|
|
cost a little more but it may save you down the road. (Besides,
|
|
if you can not afford the cost difference, you should not be building
|
|
a disk array.)</para>
|
|
|
|
<para>There are two variant of wide SCSI drives; 68-pin and 80-pin
|
|
SCA (Single Connector Attach). The SCA drives do not have a
|
|
separate 4-pin power connector, and also read the SCSI ID settings
|
|
through the 80-pin connector. If you are really serious about
|
|
building a large storage system, get SCA drives and a good SCA
|
|
enclosure (dual power supply with at least one extra fan). They
|
|
are more electronically sound than 68-pin counterparts because
|
|
there is no <quote>stub</quote> of the SCSI bus inside the disk
|
|
canister as in arrays built from 68-pin drives. They are easier
|
|
to install too (you just need to screw the drive in the canister,
|
|
instead of trying to squeeze in your fingers in a tight place to
|
|
hook up all the little cables (like the SCSI ID and disk activity
|
|
LED lines).</para>
|
|
</sect3>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>* IDE hard drives</title>
|
|
|
|
<para></para>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1>
|
|
<title>Tape drives</title>
|
|
|
|
<para><emphasis>Contributed by &a.jmb;. 2 July
|
|
1996.</emphasis></para>
|
|
|
|
<sect2>
|
|
<title>General tape access commands</title>
|
|
|
|
<para>&man.mt.1; provides generic access to the tape drives. Some of
|
|
the more common commands are <command>rewind</command>,
|
|
<command>erase</command>, and <command>status</command>. See the
|
|
&man.mt.1; manual page for a detailed description.</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Controller Interfaces</title>
|
|
|
|
<para>There are several different interfaces that support tape drives.
|
|
The interfaces are SCSI, IDE, Floppy and Parallel Port. A wide
|
|
variety of tape drives are available for these interfaces.
|
|
Controllers are discussed in <link
|
|
linkend="hw-storage-controllers">Disk/tape
|
|
controllers</link>.</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>SCSI drives</title>
|
|
|
|
<para>The &man.st.4; driver provides support for 8mm (Exabyte), 4mm
|
|
(DAT: Digital Audio Tape), QIC (Quarter-Inch Cartridge), DLT
|
|
(Digital Linear Tape), QIC Mini cartridge and 9-track (remember the
|
|
big reels that you see spinning in Hollywood computer rooms) tape
|
|
drives. See the &man.st.4; manual page for a detailed
|
|
description.</para>
|
|
|
|
<para>The drives listed below are currently being used by members of
|
|
the FreeBSD community. They are not the only drives that will work
|
|
with FreeBSD. They just happen to be the ones that we use.</para>
|
|
|
|
<sect3>
|
|
<title>4mm (DAT: Digital Audio Tape)</title>
|
|
|
|
<para><link linkend="hw-storage-python-28454">Archive Python
|
|
28454</link></para>
|
|
|
|
<para><link linkend="hw-storage-python-04687">Archive Python
|
|
04687</link></para>
|
|
|
|
<para><link linkend="hw-storage-hp1533a">HP C1533A</link></para>
|
|
|
|
<para><link linkend="hw-storage-hp1534a">HP C1534A</link></para>
|
|
|
|
<para><link linkend="hw-storage-hp35450a">HP 35450A</link></para>
|
|
|
|
<para><link linkend="hw-storage-hp35470a">HP 35470A</link></para>
|
|
|
|
<para><link linkend="hw-storage-hp35480a">HP 35480A</link></para>
|
|
|
|
<para><link linkend="hw-storage-sdt5000">SDT-5000</link></para>
|
|
|
|
<para><link linkend="hw-storage-wangtek6200">Wangtek
|
|
6200</link></para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>8mm (Exabyte)</title>
|
|
|
|
<para><link linkend="hw-storage-exb8200">EXB-8200</link></para>
|
|
|
|
<para><link linkend="hw-storage-exb8500">EXB-8500</link></para>
|
|
|
|
<para><link linkend="hw-storage-exb8505">EXB-8505</link></para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>QIC (Quarter-Inch Cartridge)</title>
|
|
|
|
<para><link linkend="hw-storage-anaconda">Archive Anaconda
|
|
2750</link></para>
|
|
|
|
<para><link linkend="hw-storage-viper60">Archive Viper
|
|
60</link></para>
|
|
|
|
<para><link linkend="hw-storage-viper150">Archive Viper
|
|
150</link></para>
|
|
|
|
<para><link linkend="hw-storage-viper2525">Archive Viper
|
|
2525</link></para>
|
|
|
|
<para><link linkend="hw-storage-tandberg3600">Tandberg TDC
|
|
3600</link></para>
|
|
|
|
<para><link linkend="hw-storage-tandberg3620">Tandberg TDC
|
|
3620</link></para>
|
|
|
|
<para><link linkend="hw-storage-tandberg3800">Tandberg TDC
|
|
3800</link></para>
|
|
|
|
<para><link linkend="hw-storage-tandberg4222">Tandberg TDC
|
|
4222</link></para>
|
|
|
|
<para><link linkend="hw-storage-wangtek5525es">Wangtek
|
|
5525ES</link></para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>DLT (Digital Linear Tape)</title>
|
|
|
|
<para><link linkend="hw-storage-dectz87">Digital TZ87</link></para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>Mini-Cartridge</title>
|
|
|
|
<para><link linkend="hw-storage-ctms3200">Conner CTMS
|
|
3200</link></para>
|
|
|
|
<para><link linkend="hw-storage-exb2501">Exabyte 2501</link></para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>Autoloaders/Changers</title>
|
|
|
|
<para><link linkend="hw-storage-hp1553a">Hewlett-Packard HP C1553A
|
|
Autoloading DDS2</link></para>
|
|
</sect3>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>* IDE drives</title>
|
|
|
|
<para></para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Floppy drives</title>
|
|
|
|
<para><link linkend="hw-storage-conner420r">Conner 420R</link></para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>* Parallel port drives</title>
|
|
|
|
<para></para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Detailed Information</title>
|
|
|
|
<sect3 id="hw-storage-anaconda">
|
|
<title>Archive Anaconda 2750</title>
|
|
|
|
<para>The boot message identifier for this drive is <literal>ARCHIVE
|
|
ANCDA 2750 28077 -003 type 1 removable SCSI 2</literal></para>
|
|
|
|
<para>This is a QIC tape drive.</para>
|
|
|
|
<para>Native capacity is 1.35GB when using QIC-1350 tapes. This
|
|
drive will read and write QIC-150 (DC6150), QIC-250 (DC6250), and
|
|
QIC-525 (DC6525) tapes as well.</para>
|
|
|
|
<para>Data transfer rate is 350kB/s using &man.dump.8;.
|
|
Rates of 530kB/s have been reported when using
|
|
Amanda</para>
|
|
|
|
<para>Production of this drive has been discontinued.</para>
|
|
|
|
<para>The SCSI bus connector on this tape drive is reversed from
|
|
that on most other SCSI devices. Make sure that you have enough
|
|
SCSI cable to twist the cable one-half turn before and after the
|
|
Archive Anaconda tape drive, or turn your other SCSI devices
|
|
upside-down.</para>
|
|
|
|
<para>Two kernel code changes are required to use this drive. This
|
|
drive will not work as delivered.</para>
|
|
|
|
<para>If you have a SCSI-2 controller, short jumper 6. Otherwise,
|
|
the drive behaves are a SCSI-1 device. When operating as a SCSI-1
|
|
device, this drive, <quote>locks</quote> the SCSI bus during some
|
|
tape operations, including: fsf, rewind, and rewoffl.</para>
|
|
|
|
<para>If you are using the NCR SCSI controllers, patch the file
|
|
<filename>/usr/src/sys/pci/ncr.c</filename> (as shown below).
|
|
Build and install a new kernel.</para>
|
|
|
|
<programlisting>*** 4831,4835 ****
|
|
};
|
|
|
|
! if (np->latetime>4) {
|
|
/*
|
|
** Although we tried to wake it up,
|
|
--- 4831,4836 ----
|
|
};
|
|
|
|
! if (np->latetime>1200) {
|
|
/*
|
|
** Although we tried to wake it up,</programlisting>
|
|
|
|
<para>Reported by: &a.jmb;</para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-python-28454">
|
|
<title>Archive Python 28454</title>
|
|
|
|
<para>The boot message identifier for this drive is <literal>ARCHIVE
|
|
Python 28454-XXX4ASB</literal> <literal>type 1 removable SCSI
|
|
2</literal> <literal>density code 0x8c, 512-byte
|
|
blocks</literal></para>
|
|
|
|
<para>This is a DDS-1 tape drive.</para>
|
|
|
|
<para>Native capacity is 2.5GB on 90m tapes.</para>
|
|
|
|
<para>Data transfer rate is XXX.</para>
|
|
|
|
<para>This drive was repackaged by Sun Microsystems as model
|
|
595-3067.</para>
|
|
|
|
<para>Reported by: Bob Bishop <email>rb@gid.co.uk</email></para>
|
|
|
|
<para>Throughput is in the 1.5 MByte/sec range, however this will
|
|
drop if the disks and tape drive are on the same SCSI
|
|
controller.</para>
|
|
|
|
<para>Reported by: Robert E. Seastrom
|
|
<email>rs@seastrom.com</email></para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-python-04687">
|
|
<title>Archive Python 04687</title>
|
|
|
|
<para>The boot message identifier for this drive is <literal>ARCHIVE
|
|
Python 04687-XXX 6580</literal> <literal>Removable Sequential
|
|
Access SCSI-2 device</literal></para>
|
|
|
|
<para>This is a DAT-DDS-2 drive.</para>
|
|
|
|
<para>Native capacity is 4GB when using 120m tapes.</para>
|
|
|
|
<para>This drive supports hardware data compression. Switch 4
|
|
controls MRS (Media Recognition System). MRS tapes have stripes
|
|
on the transparent leader. Switch 4 <emphasis>off</emphasis>
|
|
enables MRS, <emphasis>on</emphasis> disables MRS.</para>
|
|
|
|
<para>Parity is controlled by switch 5. Switch 5
|
|
<emphasis>on</emphasis> to enable parity control. Compression is
|
|
enabled with Switch 6 <emphasis>off</emphasis>. It is possible to
|
|
override compression with the <literal>SCSI MODE SELECT</literal>
|
|
command (see &man.mt.1;).</para>
|
|
|
|
<para>Data transfer rate is 800kB/s.</para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-viper60">
|
|
<title>Archive Viper 60</title>
|
|
|
|
<para>The boot message identifier for this drive is <literal>ARCHIVE
|
|
VIPER 60 21116 -007</literal> <literal>type 1 removable SCSI
|
|
1</literal></para>
|
|
|
|
<para>This is a QIC tape drive.</para>
|
|
|
|
<para>Native capacity is 60MB.</para>
|
|
|
|
<para>Data transfer rate is XXX.</para>
|
|
|
|
<para>Production of this drive has been discontinued.</para>
|
|
|
|
<para>Reported by: Philippe Regnauld
|
|
<email>regnauld@hsc.fr</email></para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-viper150">
|
|
<title>Archive Viper 150</title>
|
|
|
|
<para>The boot message identifier for this drive is <literal>ARCHIVE
|
|
VIPER 150 21531 -004</literal> <literal>Archive Viper 150 is a
|
|
known rogue</literal> <literal>type 1 removable SCSI
|
|
1</literal>. A multitude of firmware revisions exist for this
|
|
drive. Your drive may report different numbers (e.g
|
|
<literal>21247 -005</literal>.</para>
|
|
|
|
<para>This is a QIC tape drive.</para>
|
|
|
|
<para>Native capacity is 150/250MB. Both 150MB (DC6150) and 250MB
|
|
(DC6250) tapes have the recording format. The 250MB tapes are
|
|
approximately 67% longer than the 150MB tapes. This drive can
|
|
read 120MB tapes as well. It can not write 120MB tapes.</para>
|
|
|
|
<para>Data transfer rate is 100kB/s</para>
|
|
|
|
<para>This drive reads and writes DC6150 (150MB) and DC6250 (250MB)
|
|
tapes.</para>
|
|
|
|
<para>This drives quirks are known and pre-compiled into the SCSI
|
|
tape device driver (&man.st.4;).</para>
|
|
|
|
<para>Under FreeBSD 2.2-CURRENT, use <command>mt blocksize
|
|
512</command> to set the blocksize. (The particular drive had
|
|
firmware revision 21247 -005. Other firmware revisions may behave
|
|
differently) Previous versions of FreeBSD did not have this
|
|
problem.</para>
|
|
|
|
<para>Production of this drive has been discontinued.</para>
|
|
|
|
<para>Reported by: Pedro A M Vazquez
|
|
<email>vazquez@IQM.Unicamp.BR</email></para>
|
|
|
|
<para>&a.msmith;</para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-viper2525">
|
|
<title>Archive Viper 2525</title>
|
|
|
|
<para>The boot message identifier for this drive is <literal>ARCHIVE
|
|
VIPER 2525 25462 -011</literal> <literal>type 1 removable SCSI
|
|
1</literal></para>
|
|
|
|
<para>This is a QIC tape drive.</para>
|
|
|
|
<para>Native capacity is 525MB.</para>
|
|
|
|
<para>Data transfer rate is 180kB/s at 90 inches/sec.</para>
|
|
|
|
<para>The drive reads QIC-525, QIC-150, QIC-120 and QIC-24 tapes.
|
|
Writes QIC-525, QIC-150, and QIC-120.</para>
|
|
|
|
<para>Firmware revisions prior to <literal>25462 -011</literal> are
|
|
bug ridden and will not function properly.</para>
|
|
|
|
<para>Production of this drive has been discontinued.</para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-conner420r">
|
|
<title>Conner 420R</title>
|
|
|
|
<para>The boot message identifier for this drive is <literal>Conner
|
|
tape</literal>.</para>
|
|
|
|
<para>This is a floppy controller, mini cartridge tape drive.</para>
|
|
|
|
<para>Native capacity is XXXX</para>
|
|
|
|
<para>Data transfer rate is XXX</para>
|
|
|
|
<para>The drive uses QIC-80 tape cartridges.</para>
|
|
|
|
<para>Reported by: Mark Hannon
|
|
<email>mark@seeware.DIALix.oz.au</email></para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-ctms3200">
|
|
<title>Conner CTMS 3200</title>
|
|
|
|
<para>The boot message identifier for this drive is <literal>CONNER
|
|
CTMS 3200 7.00</literal> <literal>type 1 removable SCSI
|
|
2</literal>.</para>
|
|
|
|
<para>This is a mini cartridge tape drive.</para>
|
|
|
|
<para>Native capacity is XXXX</para>
|
|
|
|
<para>Data transfer rate is XXX</para>
|
|
|
|
<para>The drive uses QIC-3080 tape cartridges.</para>
|
|
|
|
<para>Reported by: Thomas S. Traylor
|
|
<email>tst@titan.cs.mci.com</email></para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-dectz87">
|
|
<title><ulink
|
|
url="http://www.digital.com/info/Customer-Update/931206004.txt.html">DEC TZ87</ulink></title>
|
|
|
|
<para>The boot message identifier for this drive is <literal>DEC
|
|
TZ87 (C) DEC 9206</literal> <literal>type 1 removable SCSI
|
|
2</literal> <literal>density code 0x19</literal></para>
|
|
|
|
<para>This is a DLT tape drive.</para>
|
|
|
|
<para>Native capacity is 10GB.</para>
|
|
|
|
<para>This drive supports hardware data compression.</para>
|
|
|
|
<para>Data transfer rate is 1.2MB/s.</para>
|
|
|
|
<para>This drive is identical to the Quantum DLT2000. The drive
|
|
firmware can be set to emulate several well-known drives,
|
|
including an Exabyte 8mm drive.</para>
|
|
|
|
<para>Reported by: &a.wilko;</para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-exb2501">
|
|
<title><ulink
|
|
url="http://www.Exabyte.COM:80/Products/Minicartridge/2501/Rfeatures.html">Exabyte EXB-2501</ulink></title>
|
|
|
|
<para>The boot message identifier for this drive is <literal>EXABYTE
|
|
EXB-2501</literal></para>
|
|
|
|
<para>This is a mini-cartridge tape drive.</para>
|
|
|
|
<para>Native capacity is 1GB when using MC3000XL
|
|
mini cartridges.</para>
|
|
|
|
<para>Data transfer rate is XXX</para>
|
|
|
|
<para>This drive can read and write DC2300 (550MB), DC2750 (750MB),
|
|
MC3000 (750MB), and MC3000XL (1GB) mini cartridges.</para>
|
|
|
|
<para>WARNING: This drive does not meet the SCSI-2 specifications.
|
|
The drive locks up completely in response to a SCSI MODE_SELECT
|
|
command unless there is a formatted tape in the drive. Before
|
|
using this drive, set the tape blocksize with</para>
|
|
|
|
<screen>&prompt.root; <userinput>mt -f /dev/st0ctl.0 blocksize 1024</userinput></screen>
|
|
|
|
<para>Before using a mini cartridge for the first time, the
|
|
mini cartridge must be formated. FreeBSD 2.1.0-RELEASE and
|
|
earlier:</para>
|
|
|
|
<screen>&prompt.root; <userinput>/sbin/scsi -f /dev/rst0.ctl -s 600 -c "4 0 0 0 0 0"</userinput></screen>
|
|
|
|
<para>(Alternatively, fetch a copy of the
|
|
<command>scsiformat</command> shell script from FreeBSD
|
|
2.1.5/2.2.) FreeBSD 2.1.5 and later:</para>
|
|
|
|
<screen>&prompt.root; <userinput>/sbin/scsiformat -q -w /dev/rst0.ctl</userinput></screen>
|
|
|
|
<para>Right now, this drive cannot really be recommended for
|
|
FreeBSD.</para>
|
|
|
|
<para>Reported by: Bob Beaulieu
|
|
<email>ez@eztravel.com</email></para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-exb8200">
|
|
<title>Exabyte EXB-8200</title>
|
|
|
|
<para>The boot message identifier for this drive is <literal>EXABYTE
|
|
EXB-8200 252X</literal> <literal>type 1 removable SCSI
|
|
1</literal></para>
|
|
|
|
<para>This is an 8mm tape drive.</para>
|
|
|
|
<para>Native capacity is 2.3GB.</para>
|
|
|
|
<para>Data transfer rate is 270kB/s.</para>
|
|
|
|
<para>This drive is fairly slow in responding to the SCSI bus during
|
|
boot. A custom kernel may be required (set SCSI_DELAY to 10
|
|
seconds).</para>
|
|
|
|
<para>There are a large number of firmware configurations for this
|
|
drive, some have been customized to a particular vendor's
|
|
hardware. The firmware can be changed via EPROM
|
|
replacement.</para>
|
|
|
|
<para>Production of this drive has been discontinued.</para>
|
|
|
|
<para>Reported by: &a.msmith;</para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-exb8500">
|
|
<title>Exabyte EXB-8500</title>
|
|
|
|
<para>The boot message identifier for this drive is <literal>EXABYTE
|
|
EXB-8500-85Qanx0 0415</literal> <literal>type 1 removable SCSI
|
|
2</literal></para>
|
|
|
|
<para>This is an 8mm tape drive.</para>
|
|
|
|
<para>Native capacity is 5GB.</para>
|
|
|
|
<para>Data transfer rate is 300kB/s.</para>
|
|
|
|
<para>Reported by: Greg Lehey <email>grog@lemis.de</email></para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-exb8505">
|
|
<title><ulink
|
|
url="http://www.Exabyte.COM:80/Products/8mm/8505XL/Rfeatures.html">Exabyte EXB-8505</ulink></title>
|
|
|
|
<para>The boot message identifier for this drive is
|
|
<literal>EXABYTE EXB-85058SQANXR1 05B0</literal> <literal>type 1
|
|
removable SCSI 2</literal></para>
|
|
|
|
<para>This is an 8mm tape drive which supports compression, and is
|
|
upward compatible with the EXB-5200 and EXB-8500.</para>
|
|
|
|
<para>Native capacity is 5GB.</para>
|
|
|
|
<para>The drive supports hardware data compression.</para>
|
|
|
|
<para>Data transfer rate is 300kB/s.</para>
|
|
|
|
<para>Reported by: Glen Foster
|
|
<email>gfoster@gfoster.com</email></para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-hp1533a">
|
|
<title>Hewlett-Packard HP C1533A</title>
|
|
|
|
<para>The boot message identifier for this drive is <literal>HP
|
|
C1533A 9503</literal> <literal>type 1 removable SCSI
|
|
2</literal>.</para>
|
|
|
|
<para>This is a DDS-2 tape drive. DDS-2 means hardware data
|
|
compression and narrower tracks for increased data
|
|
capacity.</para>
|
|
|
|
<para>Native capacity is 4GB when using 120m tapes. This drive
|
|
supports hardware data compression.</para>
|
|
|
|
<para>Data transfer rate is 510kB/s.</para>
|
|
|
|
<para>This drive is used in Hewlett-Packard's SureStore 6000eU and
|
|
6000i tape drives and C1533A DDS-2 DAT drive.</para>
|
|
|
|
<para>The drive has a block of 8 dip switches. The proper settings
|
|
for FreeBSD are: 1 ON; 2 ON; 3 OFF; 4 ON; 5 ON; 6 ON; 7 ON; 8
|
|
ON.</para>
|
|
|
|
<informaltable frame="none">
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry>switch 1</entry>
|
|
<entry>switch 2</entry>
|
|
<entry>Result</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry>On</entry>
|
|
<entry>On</entry>
|
|
<entry>Compression enabled at power-on, with host
|
|
control</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>On</entry>
|
|
<entry>Off</entry>
|
|
<entry>Compression enabled at power-on, no host
|
|
control</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>Off</entry>
|
|
<entry>On</entry>
|
|
<entry>Compression disabled at power-on, with host
|
|
control</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>Off</entry>
|
|
<entry>Off</entry>
|
|
<entry>Compression disabled at power-on, no host
|
|
control</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</informaltable>
|
|
|
|
<para>Switch 3 controls MRS (Media Recognition System). MRS tapes
|
|
have stripes on the transparent leader. These identify the tape
|
|
as DDS (Digital Data Storage) grade media. Tapes that do not have
|
|
the stripes will be treated as write-protected. Switch 3 OFF
|
|
enables MRS. Switch 3 ON disables MRS.</para>
|
|
|
|
<para>See <ulink url="http://www.hp.com/tape/c_intro.html">HP
|
|
SureStore Tape Products</ulink> and <ulink
|
|
url="http://www.impediment.com/hp/hp_technical.html">Hewlett-Packard
|
|
Disk and Tape Technical Information</ulink> for more information
|
|
on configuring this drive.</para>
|
|
|
|
<para><emphasis>Warning:</emphasis> Quality control on these drives
|
|
varies greatly. One FreeBSD core-team member has returned 2 of
|
|
these drives. Neither lasted more than 5 months.</para>
|
|
|
|
<para>Reported by: &a.se;</para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-hp1534a">
|
|
<title>Hewlett-Packard HP 1534A</title>
|
|
|
|
<para>The boot message identifier for this drive is <literal>HP
|
|
HP35470A T503</literal> <literal>type 1 removable SCSI
|
|
2</literal> <literal>Sequential-Access density code 0x13,
|
|
variable blocks</literal>.</para>
|
|
|
|
<para>This is a DDS-1 tape drive. DDS-1 is the original DAT tape
|
|
format.</para>
|
|
|
|
<para>Native capacity is 2GB when using 90m tapes.</para>
|
|
|
|
<para>Data transfer rate is 183kB/s.</para>
|
|
|
|
<para>The same mechanism is used in Hewlett-Packard's SureStore
|
|
<ulink url="http://www.dmo.hp.com/tape/sst2000.htm">2000i</ulink>
|
|
tape drive, C35470A DDS format DAT drive, C1534A DDS format DAT
|
|
drive and HP C1536A DDS format DAT drive.</para>
|
|
|
|
<para>The HP C1534A DDS format DAT drive has two indicator lights,
|
|
one green and one amber. The green one indicates tape action:
|
|
slow flash during load, steady when loaded, fast flash during
|
|
read/write operations. The amber one indicates warnings: slow
|
|
flash when cleaning is required or tape is nearing the end of its
|
|
useful life, steady indicates an hard fault. (factory service
|
|
required?)</para>
|
|
|
|
<para>Reported by Gary Crutcher
|
|
<email>gcrutchr@nightflight.com</email></para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-hp1553a">
|
|
<title>Hewlett-Packard HP C1553A Autoloading DDS2</title>
|
|
|
|
<para>The boot message identifier for this drive is "".</para>
|
|
|
|
<para>This is a DDS-2 tape drive with a tape changer. DDS-2 means
|
|
hardware data compression and narrower tracks for increased data
|
|
capacity.</para>
|
|
|
|
<para>Native capacity is 24GB when using 120m tapes. This drive
|
|
supports hardware data compression.</para>
|
|
|
|
<para>Data transfer rate is 510kB/s (native).</para>
|
|
|
|
<para>This drive is used in Hewlett-Packard's SureStore <ulink
|
|
url="http://www.dmo.hp.com/tape/sst12000.htm">12000e</ulink>
|
|
tape drive.</para>
|
|
|
|
<para>The drive has two selectors on the rear panel. The selector
|
|
closer to the fan is SCSI id. The other selector should be set to
|
|
7.</para>
|
|
|
|
<para>There are four internal switches. These should be set: 1 ON;
|
|
2 ON; 3 ON; 4 OFF.</para>
|
|
|
|
<para>At present the kernel drivers do not automatically change
|
|
tapes at the end of a volume. This shell script can be used to
|
|
change tapes:</para>
|
|
|
|
<programlisting>#!/bin/sh
|
|
PATH="/sbin:/usr/sbin:/bin:/usr/bin"; export PATH
|
|
|
|
usage()
|
|
{
|
|
echo "Usage: dds_changer [123456ne] raw-device-name
|
|
echo "1..6 = Select cartridge"
|
|
echo "next cartridge"
|
|
echo "eject magazine"
|
|
exit 2
|
|
}
|
|
|
|
if [ $# -ne 2 ] ; then
|
|
usage
|
|
fi
|
|
|
|
cdb3=0
|
|
cdb4=0
|
|
cdb5=0
|
|
|
|
case $1 in
|
|
[123456])
|
|
cdb3=$1
|
|
cdb4=1
|
|
;;
|
|
n)
|
|
;;
|
|
e)
|
|
cdb5=0x80
|
|
;;
|
|
?)
|
|
usage
|
|
;;
|
|
esac
|
|
|
|
scsi -f $2 -s 100 -c "1b 0 0 $cdb3 $cdb4 $cdb5"</programlisting>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-hp35450a">
|
|
<title>Hewlett-Packard HP 35450A</title>
|
|
|
|
<para>The boot message identifier for this drive is <literal>HP
|
|
HP35450A -A C620</literal> <literal>type 1 removable SCSI
|
|
2</literal> <literal>Sequential-Access density code
|
|
0x13</literal></para>
|
|
|
|
<para>This is a DDS-1 tape drive. DDS-1 is the original DAT tape
|
|
format.</para>
|
|
|
|
<para>Native capacity is 1.2GB.</para>
|
|
|
|
<para>Data transfer rate is 160kB/s.</para>
|
|
|
|
<para>Reported by: Mark Thompson
|
|
<email>mark.a.thompson@pobox.com</email></para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-hp35470a">
|
|
<title>Hewlett-Packard HP 35470A</title>
|
|
|
|
<para>The boot message identifier for this drive is <literal>HP
|
|
HP35470A 9 09</literal> <literal>type 1 removable SCSI
|
|
2</literal></para>
|
|
|
|
<para>This is a DDS-1 tape drive. DDS-1 is the original DAT tape
|
|
format.</para>
|
|
|
|
<para>Native capacity is 2GB when using 90m tapes.</para>
|
|
|
|
<para>Data transfer rate is 183kB/s.</para>
|
|
|
|
<para>The same mechanism is used in Hewlett-Packard's SureStore
|
|
<ulink url="http://www.dmo.hp.com/tape/sst2000.htm">2000i</ulink>
|
|
tape drive, C35470A DDS format DAT drive, C1534A DDS format DAT
|
|
drive, and HP C1536A DDS format DAT drive.</para>
|
|
|
|
<para><emphasis>Warning:</emphasis> Quality control on these drives
|
|
varies greatly. One FreeBSD core-team member has returned 5 of
|
|
these drives. None lasted more than 9 months.</para>
|
|
|
|
<para>Reported by: David Dawes
|
|
<email>dawes@rf900.physics.usyd.edu.au</email> (9 09)</para>
|
|
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-hp35480a">
|
|
<title>Hewlett-Packard HP 35480A</title>
|
|
|
|
<para>The boot message identifier for this drive is <literal>HP
|
|
HP35480A 1009</literal> <literal>type 1 removable SCSI
|
|
2</literal> <literal>Sequential-Access density code
|
|
0x13</literal>.</para>
|
|
|
|
<para>This is a DDS-DC tape drive. DDS-DC is DDS-1 with hardware
|
|
data compression. DDS-1 is the original DAT tape format.</para>
|
|
|
|
<para>Native capacity is 2GB when using 90m tapes. It cannot handle
|
|
120m tapes. This drive supports hardware data compression.
|
|
Please refer to the section on <link
|
|
linkend="hw-storage-hp1533a">HP C1533A</link> for the proper
|
|
switch settings.</para>
|
|
|
|
<para>Data transfer rate is 183kB/s.</para>
|
|
|
|
<para>This drive is used in Hewlett-Packard's SureStore <ulink
|
|
url="http://www.dmo.hp.com/tape/sst5000.htm">5000eU</ulink> and
|
|
<ulink url="http://www.dmo.hp.com/tape/sst5000.htm">5000i</ulink>
|
|
tape drives and C35480A DDS format DAT drive..</para>
|
|
|
|
<para>This drive will occasionally hang during a tape eject
|
|
operation (<command>mt offline</command>). Pressing the front
|
|
panel button will eject the tape and bring the tape drive back to
|
|
life.</para>
|
|
|
|
<para>WARNING: HP 35480-03110 only. On at least two occasions this
|
|
tape drive when used with FreeBSD 2.1.0, an IBM Server 320 and an
|
|
2940W SCSI controller resulted in all SCSI disk partitions being
|
|
lost. The problem has not be analyzed or resolved at this
|
|
time.</para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-sdt5000">
|
|
<title><ulink
|
|
url="http://www.sel.sony.com/SEL/ccpg/storage/tape/t5000.html">Sony SDT-5000</ulink></title>
|
|
|
|
<para>There are at least two significantly different models: one is
|
|
a DDS-1 and the other DDS-2. The DDS-1 version is
|
|
<literal>SDT-5000 3.02</literal>. The DDS-2 version is
|
|
<literal>SONY SDT-5000 327M</literal>. The DDS-2 version has a 1MB
|
|
cache. This cache is able to keep the tape streaming in almost
|
|
any circumstances.</para>
|
|
|
|
<para>The boot message identifier for this drive is <literal>SONY
|
|
SDT-5000 3.02</literal> <literal>type 1 removable SCSI
|
|
2</literal> <literal>Sequential-Access density code
|
|
0x13</literal></para>
|
|
|
|
<para>Native capacity is 4GB when using 120m tapes. This drive
|
|
supports hardware data compression.</para>
|
|
|
|
<para>Data transfer rate is depends upon the model or the drive. The
|
|
rate is 630kB/s for the <literal>SONY SDT-5000 327M</literal>
|
|
while compressing the data. For the <literal>SONY SDT-5000
|
|
3.02</literal>, the data transfer rate is 225kB/s.</para>
|
|
|
|
<para>In order to get this drive to stream, set the blocksize to 512
|
|
bytes (<command>mt blocksize 512</command>) reported by Kenneth
|
|
Merry <email>ken@ulc199.residence.gatech.edu</email>.</para>
|
|
|
|
<para><literal>SONY SDT-5000 327M</literal> information reported by
|
|
Charles Henrich <email>henrich@msu.edu</email>.</para>
|
|
|
|
<para>Reported by: &a.jmz;</para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-tandberg3600">
|
|
<title>Tandberg TDC 3600</title>
|
|
|
|
<para>The boot message identifier for this drive is
|
|
<literal>TANDBERG TDC 3600 =08:</literal> <literal>type 1
|
|
removable SCSI 2</literal></para>
|
|
|
|
<para>This is a QIC tape drive.</para>
|
|
|
|
<para>Native capacity is 150/250MB.</para>
|
|
|
|
<para>This drive has quirks which are known and work around code is
|
|
present in the SCSI tape device driver (&man.st.4;).
|
|
Upgrading the firmware to XXX version will fix the quirks and
|
|
provide SCSI 2 capabilities.</para>
|
|
|
|
<para>Data transfer rate is 80kB/s.</para>
|
|
|
|
<para>IBM and Emerald units will not work. Replacing the firmware
|
|
EPROM of these units will solve the problem.</para>
|
|
|
|
<para>Reported by: &a.msmith;</para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-tandberg3620">
|
|
<title>Tandberg TDC 3620</title>
|
|
|
|
<para>This is very similar to the <link
|
|
linkend="hw-storage-tandberg3600">Tandberg TDC 3600</link>
|
|
drive.</para>
|
|
|
|
<para>Reported by: &a.joerg;</para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-tandberg3800">
|
|
<title>Tandberg TDC 3800</title>
|
|
|
|
<para>The boot message identifier for this drive is
|
|
<literal>TANDBERG TDC 3800 =04Y</literal> <literal>Removable
|
|
Sequential Access SCSI-2 device</literal></para>
|
|
|
|
<para>This is a QIC tape drive.</para>
|
|
|
|
<para>Native capacity is 525MB.</para>
|
|
|
|
<para>Reported by: &a.jhs;</para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-tandberg4222">
|
|
<title>Tandberg TDC 4222</title>
|
|
|
|
<para>The boot message identifier for this drive is
|
|
<literal>TANDBERG TDC 4222 =07</literal> <literal>type 1 removable
|
|
SCSI 2</literal></para>
|
|
|
|
<para>This is a QIC tape drive.</para>
|
|
|
|
<para>Native capacity is 2.5GB. The drive will read all cartridges
|
|
from the 60 MB (DC600A) upwards, and write 150 MB (DC6150)
|
|
upwards. Hardware compression is optionally supported for the 2.5
|
|
GB cartridges.</para>
|
|
|
|
<para>This drives quirks are known and pre-compiled into the SCSI
|
|
tape device driver (&man.st.4;) beginning with FreeBSD
|
|
2.2-CURRENT. For previous versions of FreeBSD, use
|
|
<command>mt</command> to read one block from the tape, rewind the
|
|
tape, and then execute the backup program (<command>mt fsr 1; mt
|
|
rewind; dump ...</command>)</para>
|
|
|
|
<para>Data transfer rate is 600kB/s (vendor claim with compression),
|
|
350 KB/s can even be reached in start/stop mode. The rate
|
|
decreases for smaller cartridges.</para>
|
|
|
|
<para>Reported by: &a.joerg;</para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-wangtek5525es">
|
|
<title>Wangtek 5525ES</title>
|
|
|
|
<para>The boot message identifier for this drive is <literal>WANGTEK
|
|
5525ES SCSI REV7 3R1</literal> <literal>type 1 removable SCSI
|
|
1</literal> <literal>density code 0x11, 1024-byte
|
|
blocks</literal></para>
|
|
|
|
<para>This is a QIC tape drive.</para>
|
|
|
|
<para>Native capacity is 525MB.</para>
|
|
|
|
<para>Data transfer rate is 180kB/s.</para>
|
|
|
|
<para>The drive reads 60, 120, 150, and 525MB tapes. The drive will
|
|
not write 60MB (DC600 cartridge) tapes. In order to overwrite 120
|
|
and 150 tapes reliably, first erase (<command>mt erase</command>)
|
|
the tape. 120 and 150 tapes used a wider track (fewer tracks per
|
|
tape) than 525MB tapes. The <quote>extra</quote> width of the
|
|
previous tracks is not overwritten, as a result the new data lies
|
|
in a band surrounded on both sides by the previous data unless the
|
|
tape have been erased.</para>
|
|
|
|
<para>This drives quirks are known and pre-compiled into the SCSI
|
|
tape device driver (&man.st.4;).</para>
|
|
|
|
<para>Other firmware revisions that are known to work are:
|
|
M75D</para>
|
|
|
|
<para>Reported by: Marc van Kempen <email>marc@bowtie.nl</email>
|
|
<literal>REV73R1</literal> Andrew Gordon
|
|
<email>Andrew.Gordon@net-tel.co.uk</email>
|
|
<literal>M75D</literal></para>
|
|
</sect3>
|
|
|
|
<sect3 id="hw-storage-wangtek6200">
|
|
<title>Wangtek 6200</title>
|
|
|
|
<para>The boot message identifier for this drive is <literal>WANGTEK
|
|
6200-HS 4B18</literal> <literal>type 1 removable SCSI
|
|
2</literal> <literal>Sequential-Access density code
|
|
0x13</literal></para>
|
|
|
|
<para>This is a DDS-1 tape drive.</para>
|
|
|
|
<para>Native capacity is 2GB using 90m tapes.</para>
|
|
|
|
<para>Data transfer rate is 150kB/s.</para>
|
|
|
|
<para>Reported by: Tony Kimball <email>alk@Think.COM</email></para>
|
|
</sect3>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>* Problem drives</title>
|
|
|
|
<para></para>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1>
|
|
<title>CDROM drives</title>
|
|
|
|
<para><emphasis>Contributed by &a.obrien;. 23 November
|
|
1997.</emphasis></para>
|
|
|
|
<para>Generally speaking those in <emphasis>The FreeBSD
|
|
Project</emphasis> prefer SCSI CDROM drives over IDE CDROM
|
|
drives. However not all SCSI CDROM drives are equal. Some
|
|
feel the quality of some SCSI CDROM drives have been
|
|
deteriorating to that of IDE CDROM drives. Toshiba used to be
|
|
the favored stand-by, but many on the SCSI mailing list have
|
|
found displeasure with the 12x speed XM-5701TA as its volume
|
|
(when playing audio CDROMs) is not controllable by the various
|
|
audio player software.</para>
|
|
|
|
<para>Another area where SCSI CDROM manufacturers are cutting corners is
|
|
adherence to the <link linkend="scsi-further-reading">SCSI
|
|
specification</link>. Many SCSI CDROMs will respond to <link
|
|
linkend="scsi-rogue-devices">multiple LUNs</link> for its target
|
|
address. Known violators include the 6x Teac CD-56S 1.0D.</para>
|
|
</sect1>
|
|
|
|
</article>
|