* Clarify / Remove first person exposition and personal anecdotes.
PR: docs/50664
This commit is contained in:
Murray Stokely
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svn2git
2020-12-08 03:00:23 +00:00
svn path=/head/; revision=16777
1 changed files with 137 additions and 116 deletions
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@ -345,57 +345,57 @@
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<author>
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<firstname>Christopher</firstname>
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<surname>Shumway</surname>
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<contrib>Written by </contrib>
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<contrib>Original work by </contrib>
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</author>
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</authorgroup>
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<authorgroup>
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<author>
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<firstname>Valentino</firstname>
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<surname>Vaschetto</surname>
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<contrib>Marked up by </contrib>
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<contrib>Original markup by </contrib>
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</author>
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</authorgroup>
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<authorgroup>
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<author>
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<firstname>Jim</firstname>
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<surname>Brown</surname>
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<contrib>Revised by </contrib>
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</author>
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</authorgroup>
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</sect3info>
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<title>ccd (Concatenated Disk Configuration)</title>
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<title>Concatenated Disk Driver (CCD) Configuration</title>
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<para>When choosing a mass storage solution the most important
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factors to consider are speed, reliability, and cost. It is very
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rare to have all three in favor; normally a fast, reliable mass
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factors to consider are speed, reliability, and cost. It is
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rare to have all three in balance; normally a fast, reliable mass
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storage device is expensive, and to cut back on cost either speed
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or reliability must be sacrificed. In designing my system, I
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ranked the requirements by most favorable to least favorable. In
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this situation, cost was the biggest factor. I needed a lot of
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storage for a reasonable price. The next factor, speed, is not
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quite as important, since most of the usage would be over a one
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hundred megabit switched Ethernet, and that would most likely be
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the bottleneck. The ability to spread the file input/output
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operations out over several disks would be more than enough speed
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for this network. Finally, the consideration of reliability was
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an easy one to answer. All of the data being put on this mass
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storage device was already backed up on CD-R's. This drive was
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primarily here for online live storage for easy access, so if a
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drive went bad, I could just replace it, rebuild the file system,
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and copy back the data from CD-R's.</para>
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or reliability must be sacrificed.</para>
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<para>In designing the system described below, cost was chosen
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as the most important factor, followed by speed, then reliability.
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Data transfer speed for this system is ulitmately
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constrained by the network. And while reliability is very important,
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the CCD drive described below serves online data that is already
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fully backed up on CD-R's and can easily be replaced.</para>
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<para>Defining your own requirements is the first step
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in choosing a mass storage solution. If your requirements prefer
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speed or reliability over cost, your solution will differ from
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the system described in this section.</para>
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<para>To sum it up, I need something that will give me the most
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amount of storage space for my money. The cost of large IDE disks
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are cheap these days. I found a place that was selling Western
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Digital 30.7GB 5400 RPM IDE disks for about one-hundred and thirty
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US dollars. I bought three of them, giving me approximately
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ninety gigabytes of online storage.</para>
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<sect4 id="ccd-installhw">
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<title>Installing the Hardware</title>
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<para>I installed the hard drives in a system that already
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had one IDE disk in as the system disk. The ideal solution
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would be for each IDE disk to have its own IDE controller
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and cable, but without fronting more costs to acquire a dual
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IDE controller this would not be a possibility. So, I
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jumpered two disks as slaves, and one as master. One went
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on the first IDE controller as a slave to the system disk,
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and the other two where slave/master on the secondary IDE
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controller.</para>
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<para>In addition to the IDE system disk, three Western
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Digital 30GB, 5400 RPM IDE disks form the core
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of the CCD disk described below providing approximately
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90GB of online storage. Ideally,
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each IDE disk would have its own IDE controller
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and cable, but to minimize cost, additional
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IDE controllers were not used. Instead the disks were
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configured with jumpers so that each IDE controller has
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one master, and one slave.</para>
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<para>Upon reboot, the system BIOS was configured to
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automatically detect the disks attached. More importantly,
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@ -406,74 +406,75 @@ ad1: 29333MB <WDC WD307AA> [59598/16/63] at ata0-slave UDMA33
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ad2: 29333MB <WDC WD307AA> [59598/16/63] at ata1-master UDMA33
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ad3: 29333MB <WDC WD307AA> [59598/16/63] at ata1-slave UDMA33</programlisting>
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<para>At this point, if FreeBSD does not detect the disks, be
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sure that you have jumpered them correctly. I have heard
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numerous reports with problems using cable select instead of
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true slave/master configuration.</para>
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<para>The next consideration was how to attach them as part of
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the file system. I did a little research on &man.vinum.8;
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(<xref linkend="vinum-vinum">) and
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&man.ccd.4;. In this particular configuration, &man.ccd.4;
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appeared to be a better choice mainly because it has fewer
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parts. Less parts tends to indicate less chance of breakage.
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Vinum appears to be a bit of an overkill for my needs.</para>
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<note><para>If FreeBSD does not detect all the disks, ensure
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that you have jumpered them correctly. Most IDE drives
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also have a <quote>Cable Select</quote> jumper. This is
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<emphasis>not</emphasis> the jumper for the master/slave
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relationship. Consult the drive documentation for help in
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identifying the correct jumper.</para></note>
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<para>Next, consider how to attach them as part of the file
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system. You should research both &man.vinum.8; (<xref
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linkend="vinum-vinum">) and &man.ccd.4;. In this
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particular configuration, &man.ccd.4; was chosen.</para>
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</sect4>
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<sect4 id="ccd-setup">
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<title>Setting up the CCD</title>
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<para><application>CCD</application> allows me to take
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several identical disks and concatenate them into one
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logical file system. In order to use
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<application>ccd</application>, I need a kernel with
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<application>ccd</application> support built into it. I
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added this line to my kernel configuration file and rebuilt
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the kernel:</para>
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<para><application>CCD</application> allows you to take
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several identical disks and concatenate them into one
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logical file system. In order to use
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<application>ccd</application>, you need a kernel with
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<application>ccd</application> support built in.
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Add this line to your kernel configuration file, rebuild, and
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reinstall the kernel:</para>
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<programlisting>pseudo-device ccd 4</programlisting>
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<note><para>In FreeBSD 5.0, it is not necessary to specify
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a number of ccd devices, as the ccd device driver is now
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cloning -- new device instances will automatically be
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self-cloning -- new device instances will automatically be
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created on demand.</para></note>
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<para><application>ccd</application> support can also be
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loaded as a kernel loadable module in FreeBSD 4.0 or
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loaded as a kernel loadable module in FreeBSD 3.0 or
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later.</para>
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<para>To set up <application>ccd</application>, first I need
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to disklabel the disks. Here is how I disklabeled
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them:</para>
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<para>To set up <application>ccd</application>, you must first use
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&man.disklabel.8 to label the disks:</para>
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<programlisting>disklabel -r -w ad1 auto
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disklabel -r -w ad2 auto
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disklabel -r -w ad3 auto</programlisting>
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<para>This created a disklabel ad1c, ad2c and ad3c that
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spans the entire disk.</para>
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<para>This creates a disklabel for ad1c, ad2c and ad3c that
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spans the entire disk.</para>
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<para>The next step is to change the disklabel type. To do
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that I had to edit the disklabel:</para>
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<para>The next step is to change the disklabel type. You
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can use <application>disklabel</application> to edit the
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disks:</para>
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<programlisting>disklabel -e ad1
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disklabel -e ad2
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disklabel -e ad3</programlisting>
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<para>This opened up the current disklabel on each disk
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respectively in whatever editor the <envar>EDITOR</envar>
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environment variable was set to, in my case, &man.vi.1;.
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Inside the editor I had a section like this:</para>
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<para>This opens up the current disklabel on each disk with
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the editor specified by the <envar>EDITOR</envar>
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environment variable, typically &man.vi.1;.</para>
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<para>An unmodified disklabel will look something like
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this:</para>
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<programlisting>8 partitions:
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# size offset fstype [fsize bsize bps/cpg]
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c: 60074784 0 unused 0 0 0 # (Cyl. 0 - 59597)</programlisting>
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<para>I needed to add a new "e" partition for &man.ccd.4; to
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use. This usually can be copied of the "c" partition, but
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the <option>fstype</option> must be <userinput>4.2BSD</userinput>.
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Once I was done,
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my disklabel should look like this:</para>
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<para>Add a new "e" partition for &man.ccd.4; to use. This
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can usually be copied from the <quote>c</quote> partition,
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but the <option>fstype</option> <emphasis>must</emphasis>
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be <userinput>4.2BSD</userinput>. The disklabel should
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now look something like this:</para>
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<programlisting>8 partitions:
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# size offset fstype [fsize bsize bps/cpg]
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@ -485,12 +486,7 @@ disklabel -e ad3</programlisting>
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<sect4 id="ccd-buildingfs">
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<title>Building the File System</title>
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<para>Now that I have all of the disks labeled, I needed to
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build the <application>ccd</application>. To do that, I
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used a utility called &man.ccdconfig.8;.
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<command>ccdconfig</command> takes several arguments, the
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first argument being the device to configure, in this case,
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<devicename>/dev/ccd0c</devicename>. The device node for
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<para>The device node for
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<devicename>ccd0c</devicename> may not exist yet, so to
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create it, perform the following commands:</para>
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@ -501,58 +497,79 @@ sh MAKEDEV ccd0</programlisting>
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manage device nodes in <filename>/dev</filename>, so use of
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<command>MAKEDEV</command> is not necessary.</para></note>
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<para>The next argument <command>ccdconfig</command> expects
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is the interleave for the file system. The interleave
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defines the size of a stripe in disk blocks, normally five
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hundred and twelve bytes. So, an interleave of thirty-two
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would be sixteen thousand three hundred and eighty-four
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bytes.</para>
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<para>Now that you have all of the disks labeled, you must
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build the <application>ccd</application>. To do that,
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use &man.ccdconfig.8;, with options similar to the following:
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<para>After the interleave comes the flags for
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<command>ccdconfig</command>. If you want to enable drive
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mirroring, you can specify a flag here. In this
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configuration, I am not mirroring the
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<application>ccd</application>, so I left it as zero.</para>
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<programlisting>ccdconfig ccd0<co id="co-ccd-dev"> 32<co id="co-ccd-interleave"> 0<co id="co-ccd-flags"> /dev/ad1e<co id="co-ccd-devs"> /dev/ad2e /dev/ad3e</programlisting>
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<para>The final arguments to <command>ccdconfig</command>
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are the devices to place into the array. Putting it all
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together I get this command:</para>
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The use and meaning of each option is shown below:</para>
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<programlisting>ccdconfig ccd0 32 0 /dev/ad1e /dev/ad2e /dev/ad3e</programlisting>
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<calloutlist>
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<callout arearefs="co-ccd-dev">
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<para>The first argument is the device to configure, in this case,
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<devicename>/dev/ccd0c</devicename>. The <filename>/dev/</filename>
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portion is optional.</para>
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</callout>
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<para>This configures the <application>ccd</application>.
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I can now &man.newfs.8; the file system.</para>
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<callout arearefs="co-ccd-interleave">
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<para>The interleave for the file system. The interleave
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defines the size of a stripe in disk blocks, each normally 512 bytes.
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So, an interleave of 32 would be 16,384 bytes.</para>
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</callout>
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<callout arearefs="co-ccd-flags">
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<para>Flags for <command>ccdconfig</command>. If you want to enable drive
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mirroring, you can specify a flag here. This
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configuration does not provide mirroring for
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<application>ccd</application>, so it is set at 0 (zero).</para>
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</callout>
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<callout arearefs="co-ccd-devs">
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<para>The final arguments to <command>ccdconfig</command>
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are the devices to place into the array. Use the complete pathname
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for each device.</para>
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</callout>
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</calloutlist>
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<para>After running <command>ccdconfig</command> the <application>ccd</application>
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is configured. A file system can be installed. Refer to &man.newfs.8;
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for options, or simply run: </para>
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<programlisting>newfs /dev/ccd0c</programlisting>
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</sect4>
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<sect4 id="ccd-auto">
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<title>Making it all Automatic</title>
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<para>Finally, if I want to be able to mount the
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<application>ccd</application>, I need to
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configure it first. I write out my current configuration to
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<para>Generally, you will want to mount the
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<application>ccd</application> upon each reboot. To do this, you must
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configure it first. Write out your current configuration to
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<filename>/etc/ccd.conf</filename> using the following command:</para>
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<programlisting>ccdconfig -g > /etc/ccd.conf</programlisting>
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<para>When I reboot, the script <command>/etc/rc</command>
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runs <command>ccdconfig -C</command> if /etc/ccd.conf
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<para>During reboot, the script <command>/etc/rc</command>
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runs <command>ccdconfig -C</command> if <filename>/etc/ccd.conf</filename>
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exists. This automatically configures the
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<application>ccd</application> so it can be mounted.</para>
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<para>If you are booting into single user mode, before you can
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<note><para>If you are booting into single user mode, before you can
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<command>mount</command> the <application>ccd</application>, you
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need to issue the following command to configure the
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array:</para>
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<programlisting>ccdconfig -C</programlisting>
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</note>
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<para>Then, we need an entry for the
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<application>ccd</application> in
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<para>To automatically mount the <application>ccd</application>,
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place an entry for the <application>ccd</application> in
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<filename>/etc/fstab</filename> so it will be mounted at
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boot time.</para>
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boot time:</para>
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<programlisting>/dev/ccd0c /media ufs rw 2 2</programlisting>
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</sect4>
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@ -569,7 +586,7 @@ sh MAKEDEV ccd0</programlisting>
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storage. &man.vinum.8; implements the RAID-0, RAID-1 and
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RAID-5 models, both individually and in combination.</para>
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<para>See the <xref linkend="vinum-vinum"> for more
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<para>See <xref linkend="vinum-vinum"> for more
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information about &man.vinum.8;.</para>
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</sect3>
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</sect2>
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@ -581,16 +598,19 @@ sh MAKEDEV ccd0</programlisting>
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<primary>RAID</primary>
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<secondary>Hardware</secondary>
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</indexterm>
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<para>FreeBSD also supports a variety of hardware <acronym>RAID</acronym>
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controllers. In which case the actual <acronym>RAID</acronym> system
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is built and controlled by the card itself. Using an on-card
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<acronym>BIOS</acronym>, the card will control most of the disk operations
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itself. The following is a brief setup using a Promise <acronym>IDE RAID</acronym>
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controller. When this card is installed and the system started up, it will
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display a prompt requesting information. Follow the on screen instructions
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to enter the cards setup screen. From here a user should have the ability to
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combine all the attached drives. When doing this, the disk(s) will look like
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a single drive to FreeBSD. Other <acronym>RAID</acronym> levels can be setup
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controllers. These devices control a <acronym>RAID</acronym> subsystem
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without the need for FreeBSD specific software to manage the
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array.</para>
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<para>Using an on-card <acronym>BIOS</acronym>, the card controls most of the disk operations
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itself. The following is a brief setup description using a <acronym>Promise IDE RAID</acronym>
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controller. When this card is installed and the system is started up, it
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displays a prompt requesting information. Follow the instructions
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to enter the card's setup screen. From here, you have the ability to
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combine all the attached drives. After doing so, the disk(s) will look like
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a single drive to FreeBSD. Other <acronym>RAID</acronym> levels can be set up
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accordingly.
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</para>
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</sect2>
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@ -611,7 +631,7 @@ ata3: resetting devices .. done
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ad6: hard error reading fsbn 1116119 of 0-7 (ad6 bn 1116119; cn 1107 tn 4 sn 11) status=59 error=40
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ar0: WARNING - mirror lost</programlisting>
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<para>Using &man.atacontrol.8;, check to see how things look:</para>
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<para>Using &man.atacontrol.8;, check for further information:</para>
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<screen>&prompt.root; <userinput>atacontrol list</userinput>
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ATA channel 0:
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@ -659,8 +679,9 @@ Slave: no device present</screen>
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</step>
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<step>
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<para>The rebuild command hangs until complete, its possible to open another
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terminal and check on the progress by issuing the following command:</para>
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<para>The rebuild command hangs until complete. However, it is possible to open another
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terminal (using <keycombo action="simul"><keycap>Alt</keycap> <keycap>F<replaceable>n</replaceable></keycap></keycombo>)
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and check on the progress by issuing the following command:</para>
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<screen>&prompt.root; <userinput>dmesg | tail -10</userinput>
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[output removed]
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