Added sect1 on ccd
Reviewed by: chern
This commit is contained in:
Valentino Vaschetto
parent
bfe5032a69
commit
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Notes:
svn2git
2020-12-08 03:00:23 +00:00
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1 changed files with 202 additions and 1 deletions
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@ -1,7 +1,7 @@
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<!--
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The FreeBSD Documentation Project
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$FreeBSD: doc/en_US.ISO8859-1/books/handbook/disks/chapter.sgml,v 1.53 2001/08/19 23:58:56 dd Exp $
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$FreeBSD: doc/en_US.ISO8859-1/books/handbook/disks/chapter.sgml,v 1.54 2001/08/22 06:32:24 murray Exp $
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-->
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<chapter id="disks">
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@ -1294,6 +1294,207 @@ scsibus1:
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audio tracks, controlling the speed, and other things.</para>
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</sect2>
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</sect1>
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<sect1 id="ccd">
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<sect1info>
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<authorgroup>
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<author>
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<firstname>Chris</firstname>
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<surname>Shumway</surname>
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<contrib>Written 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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</author>
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</authorgroup>
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</sect1info>
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<title>ccd (Concatenated Disk Configuration)</title>
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<para>It seems like today everyone has a collection of multimedia
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files. Everything from mp3's to video clips. I've converted most
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of my audio CDROM collection to mp3's so I can have all of my music
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in one centralized location, and not have to hunt down the audio CD
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with that one song I got stuck in my head. The problem I was faced
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with is where to store all these files?</para>
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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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storage device is expensive, and to cut back on cost either speed or
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reliability must be sacrificed. In designing my system, I ranked
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the requirements by most favorable to least favorable. In this
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situation, cost was the biggest factor. I needed a lot of storage
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for a reasonable price. The next factor, speed, is not quite as
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important, since most of the usage would be over a one hundred
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megabit switched Ethernet, and that would most likely be the
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bottleneck. The ability to spread the file input/output operations
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out over several disks would be more than enough speed for this
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network. Finally, the consideration of reliability was an easy one
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to answer. All of the data being put on this mass storage device
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was already backed up on CD-R's. This drive was primarily here for
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online live storage for easy access, so if a drive went bad, I could
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just replace it, rebuild the filesystem, and copy back the data from
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CD-R's.</para>
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<para>To sum it up, I need something that will give
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me the most amount of storage space for my money. The cost of large
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IDE disks are cheap these days. I found a place that was selling
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Western Digital 30.7gb 5400 RPM IDE disks for about one-hundred and
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thirty US dollars. I bought three of them, giving me approximately
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ninety gigabytes of online storage.</para>
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<sect2 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 had
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one IDE disk in as the system disk. The ideal solution would be
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for each IDE disk to have its own IDE controller and cable, but
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without fronting more costs to acquire a dual IDE controller
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this wouldn't be a possibility. So, I jumpered two disks as
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slaves, and one as master. One went on the first IDE controller
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as a slave to the system disk, and the other two where
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slave/master on the secondary IDE controller.</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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FreeBSD detected them on reboot:</para>
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<programlisting>ad0: 19574MB <WDC WD205BA> [39770/16/63] at ata0-master UDMA33
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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 doesn't 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 the
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filesystem. I did a little research on
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<ulink url="http://www.vinumvm.org">&man.vinum.8;</ulink> and FreeBSD's &man.ccd.4;.
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In this particular configuration, &man.ccd.4; appeared to be a better
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choice mainly because it has fewer parts. Less parts tends to
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indicate less chance of breakage. Vinum appears to be a bit of an
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overkill for my needs.</para>
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</sect2>
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<sect2 id="ccd-setup">
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<title>Setting up the CCD</title>
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<para>CCD allows me to take several identical disks and
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concatenate them into one logical filesystem. In order to use
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ccd, I need a kernel with ccd support built into it. I added
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this line to my kernel configuration file and rebuilt the
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kernel:</para>
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<programlisting>pseudo-device ccd 4</programlisting>
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<para>Ccd support can also be loaded as a kernel loadable module
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in FreeBSD 4.0 or later.</para>
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<para>To set up ccd, first I need to disklabel the disks.
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Here's how I disklabeled them:</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 spans
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the entire disk.</para>
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<para>The next step is to change the disklabel type. To do that
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I had to edit the disklabel:</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> environment variable
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was set to, in my case, &man.vi.1;. Inside the editor I had a
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section 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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c: 60074784 0 unused 0 0 0 # (Cyl. 0 - 59597)</programlisting>
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<para>I need to add a new "e" partition for &man.ccd.4; to use. This
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can be a copy of the "c" partition. Once I was done, my
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disklabel shoud look 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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c: 60074784 0 unused 0 0 0 # (Cyl. 0 - 59597)
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e: 60074784 0 unused 0 0 0 # (Cyl. 0 - 59597)</programlisting>
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</sect2>
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<sect2 id="ccd-buildingfs">
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<title>Building the Filesystem</title>
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<para>Now that I have all of the disks labeled, I needed to
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build the ccd. To do that, I used a utility called
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&man.ccdconfig.8;. <command>ccdconfig</command> takes several arguments, the first
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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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<devicename>ccd0c</devicename> may not exsist yet, so to create
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it, preform the following commands:</para>
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<programlisting>cd /dev
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sh MAKEDEV ccd0</programlisting>
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<para>The next argument <command>ccdconfig</command> expects is the interleave
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for the filesystem. The interleave defines the size of a
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stripe in disk blocks, normally five hundred and twelve bytes.
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So, an interleave of thirty-two would be sixteen thousand
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three hundred and eighty-four bytes.</para>
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<para>After the interleave comes the flags for <command>ccdconfig</command>. If
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you want to enable drive mirroring, you can specificy a flag
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here. In this configuration, I am not mirroring the ccd, so I
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left it as zero.</para>
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<para>The final arguments to <command>ccdconfig</command> are the devices to place
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into the array. Putting it all together I get this
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command:</para>
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<programlisting>ccdconfig ccd0 32 0 /dev/ad1c /dev/ad2c /dev/ad3c</programlisting>
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<para>This configures the ccd. I can now &man.newfs.8; the filesystem.</para>
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<programlisting>newfs /dev/ccd0c</programlisting>
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</sect2>
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<sect2 id="ccd-auto">
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<title>Making It All Automagic</title>
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<para>Finally, if I want to be able to mount the ccd, I need to
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configure it first. I write out my 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> runs
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<command>ccdconfig -C</command> if /etc/ccd.conf exists. This
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automatically configures the ccd 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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<command>mount</command> the ccd, you need to issue the following command to
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configure the array:</para>
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<programlisting>ccdconfig -C</programlisting>
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<para>Then, we need an entry for the ccd in <filename>/etc/fstab</filename> so it
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will be mounted at boot time.</para>
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<programlisting>/dev/ccd0c /media ufs rw 2 2</programlisting>
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</sect2>
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</sect1>
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</chapter>
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<!--
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