LDP/LDP/faq/docbook/Linux-RAID-FAQ.xml

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 <artheader>
  <title>Linux-RAID FAQ</title>

  <author>
     <firstname>Gregory</firstname>
     <surname>Leblanc</surname>
     <affiliation>
        <address>
           <email>gleblanc (at) cu-portland.edu</email>
        </address>
     </affiliation>
  </author>

   <revhistory>

   <revision>
    <revnumber>v0.0.7</revnumber>
    <date>22 August 2000</date>
    <authorinitials>gml</authorinitials>
    <revremark>
     vger isn't at rutgers anymore, so I'm making a few changes.  Talked with Dave (maintainer of vger) about getting something into the welcome message, and/or footer of messages
    </revremark>

   <revision>
    <revnumber>v0.0.6</revnumber>
    <date>14 August 2000</date>
    <authorinitials>gml</authorinitials>
    <revremark>
     Clarified the section on determining whether or not the RAID patches have been applied.  Modules only serve to make life more dificult.  Thanks to Brent J. Nordquist [bjn (at) visi.com]</revremark>
   </revision>

  </revhistory>


  <abstract>
    <para>This is a FAQ for the Linux-RAID mailing list, hosted on vger.kernel.org.  vger.rutgers.edu is gone, so don't bother looking for it.  It's intended as a supplement to the existing Linux-RAID HOWTO, to cover questions that keep occurring on the mailing list.  PLEASE read this document before your post to the list.</para>

  </abstract>

 </artheader>

   <qandaset>

   <qandadiv>
    <title>General</title>

    <qandaentry>
     <question>
     <para>Where can I find archives for the linux-raid mailing list?</para>
    </question>
    <answer>
     <para>My favorite archives are at <ulink url="http://www.geocrawler.com/lists/3/Linux/57/0/">http://www.geocrawler.com/lists/3/Linux/57/0/</ulink>.</para>
     <para>Other archives are available at <ulink url="http://marc.theaimsgroup.com/?l=linux-raid&amp;r=1&amp;w=2">http://marc.theaimsgroup.com/?l=linux-raid&amp;r=1&amp;w=2</ulink></para>
      <para>Another archive site is <ulink url="http://www.mail-archive.com/linux-raid@vger.rutgers.edu/">http://www.mail-archive.com/linux-raid@vger.rutgers.edu/</ulink></para>
    </answer>
   </qandaentry>

   <qandaentry>
    <question>
     <para>Where can I find the latest version of this FAQ?</para>
    </question>

    <answer>
     <para>The latest version of this FAQ will be available from the LDP website, at <ulink url="http://www.LinuxDoc.org/FAQ/">http://www.LinuxDoc.org/FAQ/</ulink>.  As soon as I get my server at home fixed, I'll make it available there as well.</para>
    </answer>
   </qandaentry>

   </qandadiv>


   <qandadiv>
    <title>Kernel</title>

    <qandaentry>
     <question>
     <para>I'm running <replaceable>[insert your linux distribution here]</replaceable>.  Do I need to patch my kernel to make RAID work?</para>
     </question>
     <answer>
      <para>Well, the short answer is, it depends.  Distributions that are keeping up to date have the RAID patches included in their kernels.  The kernel that RedHat distributes, as do some others.  If you download a 2.2.x kernel from ftp.kernel.org, then you will need to patch your kernel.</para>
     </answer>
    </qandaentry>

    <qandaentry>

     <question>
      <para>How can I tell if I need to patch my kernel?</para>
     </question>

     <answer>
     <para>The easiest way is to check what's in <filename>/proc/mdstat</filename>.  Here's a sample from a 2.2.x kernel, <emphasis>with</emphasis> the RAID patches applied.

      <screen format="linespecific"> 

[gleblanc@grego1 gleblanc]$ cat /proc/mdstat
Personalities : [linear] [raid0] [raid1] [raid5] [translucent]
read_ahead not set
unused devices: &lt;none&gt;
      </screen>

If the contents of <filename>/proc/mdstat</filename> looks like the above, then you don't need to patch your kernel.</para>
     <para>The "Personalities" line in your kernel may not look exactly like the above, if you have RAID compiled as modules.  Most distributions will have RAID compiled as modules to save space on the boot diskette.  If you're not using any RAID sets, then you will probably see a blank space at the end of the "Personalities" line, don't worry, that just means that the RAID modules aren't loaded yet.</para>

     <para>Here's a sample from a 2.2.x kernel, <emphasis>without</emphasis> the RAID patches applied.

      <screen format="linespecific">

[root@serek ~]# cat /proc/mdstat 
Personalities : [1 linear] [2 raid0] 
read_ahead not set 
md0 : inactive 
md1 : inactive 
md2 : inactive 
md3 : inactive 

      </screen>

<emphasis>If your <filename>/proc/mdstat</filename> looks like this one, then you need to patch your kernel.</emphasis></para>

     </answer>

    </qandaentry>

    <qandaentry>

     <question>
      <para>Where can I get the latest RAID patches for my kernel?</para>
     </question>

     <answer>

      <para>The patches for the 2.2.x kernels up to, and including, 2.2.13 are available from <ulink url="ftp://ftp.kernel.org/pub/linux/daemons/raid/alpha/">ftp.kernel.org</ulink>.  Use the kernel patch that most closely matches your kernel revision.  For example, the 2.2.11 patch can also be used on 2.2.12 and 2.2.13.</para>
      <para>The patches for 2.2.14 and later kernels are at <ulink url="http://people.redhat.com/mingo/raid-patches/">http://people.redhat.com/mingo/raid-patches/</ulink>.  Use the right patch for your kernel, these patches haven't worked on other kernel revisions yet.  Please use something like wget/curl/lftp to retrieve this patch, as it's easier on the server than using a client like Netscape.  Downloading patches with Lynx has been unsuccessful for me; wget may be the easiest way.</para>
     </answer>

    </qandaentry>

    <qandaentry>

     <question>
      <para>How do I apply the patch to a kernel that I just downloaded from ftp.kernel.org?</para>
     </question>

     <answer>

     <para>First, unpack the kernel into some directory, generally people use <filename class="directory">/usr/src/linux</filename>.  Change to this directory, and type <command>patch -p1 &lt; /path/to/raid-version.patch</command>.

      <informalexample>

       <para>On my RedHat 6.2 system, I decompressed the 2.2.16 kernel into <filename class="directory">/usr/src/linux-2.2.16</filename>.  From <filename class="directory">/usr/src/linux-2.2.16</filename>, I type in <command>patch -p1 &lt; <replaceable>/home/gleblanc/raid-2.2.16-A0</replaceable></command>.  Then I rebuild the kernel using <command>make menuconfig</command> and related builds.</para>
      </informalexample>

     </para>

    </answer>

   </qandaentry>

   <qandaentry>

    <question>
     <para>What kind of drives can I use RAID with?  Do only SCSI or IDE drives work?  Do I need different patches for different kinds of drives?</para>
    </question>

    <answer>
     <para>Software RAID works with any block device in the Linux kernel.  This includes IDE and SCSI drives, as well as most harware RAID controllers.  There are no different patches for IDE drives vs SCSI drives.</para>
    </answer>
   </qandaentry>

  </qandadiv>


  <qandadiv>
   <title>RAIDtools</title>

   <qandaentry>

    <question>
     <para>Why are the RAIDtools at <ulink url="http://people.redhat.com/mingo/raid-patches/">http://people.redhat.com/mingo/raid-patches/</ulink> labeled <emphasis>dangerous</emphasis>, and if they're dangerous, should I use them?</para>
    </question>

    <answer>
     <para>The tools are labeled <emphasis>dangerous</emphasis> because the RAID code isn't part of the <quote>stable</quote> Linux kernel.</para>
     <para>The tools found at the above URL are the latest and greatest.  You <emphasis>should</emphasis> use these tools with the kernel patches from the same location.</para>
    </answer>

   </qandaentry>

  </qandadiv>

 </qandaset>

</article>


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