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157
LDP/faq/docbook/Linux-RAID-FAQ.sgml
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@ -22,7 +22,8 @@
<date>6 September 2000</date>
<authorinitials>gml</authorinitials>
<revremark>
The info/welcome message on vger.kernel.org has a pointer to this FAQ. New section on recovery, and fixed a few markup things.
The info/welcome message on vger.kernel.org has a pointer to this
FAQ. New section on recovery, and fixed a few markup things.
</revremark>
</revision>
@ -31,7 +32,9 @@
<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
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>
@ -39,7 +42,12 @@
<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>
<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>
@ -52,12 +60,16 @@
<qandaentry>
<question>
<para>Where can I find archives for the linux-raid mailing list?</para>
<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>
<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>
@ -67,7 +79,11 @@
</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>
<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>
@ -79,10 +95,16 @@
<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>
<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>
<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>
@ -93,7 +115,9 @@
</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.
<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">
@ -103,8 +127,15 @@ 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>
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.
@ -120,7 +151,8 @@ md3 : inactive
</screen>
<emphasis>If your <filename>/proc/mdstat</filename> looks like this one, then you need to patch your kernel.</emphasis></para>
<emphasis>If your <filename>/proc/mdstat</filename> looks like this
one, then you need to patch your kernel.</emphasis></para>
</answer>
@ -134,8 +166,20 @@ md3 : inactive
<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>
<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>
@ -148,11 +192,21 @@ md3 : inactive
<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>.
<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>
<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>
@ -164,11 +218,16 @@ md3 : inactive
<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>
<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>
<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>
@ -181,12 +240,19 @@ md3 : inactive
<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>
<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>
<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>
@ -199,12 +265,18 @@ md3 : inactive
<qandaentry>
<question>
<para>How can I tell if one of the disks in my RAID array has failed?</para>
<para>How can I tell if one of the disks in my RAID array has
failed?</para>
</question>
<answer>
<para>A couple of things should indicate when a disk has failed. There should be quite a few messages in <filename>/var/log/messages</filename> indicating errors accessing that device, which should be a good indication that something is wrong.</para>
<para>You should also notice that your <filename>/proc/mdstat</filename> looks different. Here's a snip from a good /proc/mdstat
<para>A couple of things should indicate when a disk has failed.
There should be quite a few messages in
<filename>/var/log/messages</filename> indicating errors
accessing that device, which should be a good indication that
something is wrong.</para> <para>You should also notice that your
<filename>/proc/mdstat</filename> looks different. Here's a snip
from a good /proc/mdstat
<screen format="linespecific">
@ -216,7 +288,8 @@ unused devices: &lt;none&gt;
</screen>
</para>
<para>And here's one from a <filename>/proc/mdstat</filename> where one of the RAID sets has a missing disk.
<para>And here's one from a <filename>/proc/mdstat</filename>
where one of the RAID sets has a missing disk.
<screen format="linespecific">
@ -228,7 +301,12 @@ unused devices: &lt;none&gt;
</screen>
</para>
<para>I don't know if <filename>/proc/mdstat</filename> will reflect the status of a HOT SPARE. If you have set one up, you should be watching <filename>/var/log/messages</filename> for any disk failures. I'd like to get some logs of a disk failure, and <filename>/proc/mdstat</filename> from a system with a hot spare.</para>
<para>I don't know if <filename>/proc/mdstat</filename> will
reflect the status of a HOT SPARE. If you have set one up, you
should be watching <filename>/var/log/messages</filename> for any
disk failures. I'd like to get some logs of a disk failure, and
<filename>/proc/mdstat</filename> from a system with a hot
spare.</para>
</answer>
</qandaentry>
@ -240,8 +318,16 @@ unused devices: &lt;none&gt;
</question>
<answer>
<para>RAID generally doesn't mark a disk as bad unless it is, so you probably need a new disk. Most disks have a 3 year warranty, but some good SCSI hard drives may have a 5 year warranty. See if you can get the manufacturer to replace the failed disk for you.</para>
<para>When you get the new disk, power down the system, and install it, then partition the drive so that it has partitions the size of your missing RAID partitions. After you're finished partitioning the disk, use the command <command>raidhotadd</command> to put the new disk into the array and begin reconstruction.</para>
<para>RAID generally doesn't mark a disk as bad unless it is, so
you probably need a new disk. Most disks have a 3 year warranty,
but some good SCSI hard drives may have a 5 year warranty. See
if you can get the manufacturer to replace the failed disk for
you.</para> <para>When you get the new disk, power down the
system, and install it, then partition the drive so that it has
partitions the size of your missing RAID partitions. After
you're finished partitioning the disk, use the command
<command>raidhotadd</command> to put the new disk into the array
and begin reconstruction.</para>
</answer>
</qandaentry>
@ -249,11 +335,18 @@ unused devices: &lt;none&gt;
<qandaentry>
<question>
<para><command>dmesg</command> shows <quote>md: serializing resync, md4 has overlapping physical units with md5</quote>. What does this mean?</para>
<para><command>dmesg</command> shows <quote>md: serializing
resync, md4 has overlapping physical units with md5</quote>.
What does this mean?</para>
</question>
<answer>
<para>In that message <quote>physical units</quote> refers to disks, and not to blocks on the disks. Since there is more than 1 RAID array that needs resyncing on a disk, the RAID code is going to sync md4 first, and md5 second, to avoid excessive seeks (also called thrashing), which would drastically slow the resync process.</para>
<para>In that message <quote>physical units</quote> refers to
disks, and not to blocks on the disks. Since there is more than
1 RAID array that needs resyncing on a disk, the RAID code is
going to sync md4 first, and md5 second, to avoid excessive seeks
(also called thrashing), which would drastically slow the resync
process.</para>
</answer>
</qandaentry>

157
LDP/faq/docbook/Linux-RAID-FAQ.xml
View File

@ -22,7 +22,8 @@
<date>6 September 2000</date>
<authorinitials>gml</authorinitials>
<revremark>
The info/welcome message on vger.kernel.org has a pointer to this FAQ. New section on recovery, and fixed a few markup things.
The info/welcome message on vger.kernel.org has a pointer to this
FAQ. New section on recovery, and fixed a few markup things.
</revremark>
</revision>
@ -31,7 +32,9 @@
<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
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>
@ -39,7 +42,12 @@
<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>
<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>
@ -52,12 +60,16 @@
<qandaentry>
<question>
<para>Where can I find archives for the linux-raid mailing list?</para>
<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>
<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>
@ -67,7 +79,11 @@
</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>
<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>
@ -79,10 +95,16 @@
<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>
<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>
<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>
@ -93,7 +115,9 @@
</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.
<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">
@ -103,8 +127,15 @@ 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>
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.
@ -120,7 +151,8 @@ md3 : inactive
</screen>
<emphasis>If your <filename>/proc/mdstat</filename> looks like this one, then you need to patch your kernel.</emphasis></para>
<emphasis>If your <filename>/proc/mdstat</filename> looks like this
one, then you need to patch your kernel.</emphasis></para>
</answer>
@ -134,8 +166,20 @@ md3 : inactive
<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>
<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>
@ -148,11 +192,21 @@ md3 : inactive
<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>.
<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>
<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>
@ -164,11 +218,16 @@ md3 : inactive
<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>
<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>
<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>
@ -181,12 +240,19 @@ md3 : inactive
<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>
<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>
<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>
@ -199,12 +265,18 @@ md3 : inactive
<qandaentry>
<question>
<para>How can I tell if one of the disks in my RAID array has failed?</para>
<para>How can I tell if one of the disks in my RAID array has
failed?</para>
</question>
<answer>
<para>A couple of things should indicate when a disk has failed. There should be quite a few messages in <filename>/var/log/messages</filename> indicating errors accessing that device, which should be a good indication that something is wrong.</para>
<para>You should also notice that your <filename>/proc/mdstat</filename> looks different. Here's a snip from a good /proc/mdstat
<para>A couple of things should indicate when a disk has failed.
There should be quite a few messages in
<filename>/var/log/messages</filename> indicating errors
accessing that device, which should be a good indication that
something is wrong.</para> <para>You should also notice that your
<filename>/proc/mdstat</filename> looks different. Here's a snip
from a good /proc/mdstat
<screen format="linespecific">
@ -216,7 +288,8 @@ unused devices: &lt;none&gt;
</screen>
</para>
<para>And here's one from a <filename>/proc/mdstat</filename> where one of the RAID sets has a missing disk.
<para>And here's one from a <filename>/proc/mdstat</filename>
where one of the RAID sets has a missing disk.
<screen format="linespecific">
@ -228,7 +301,12 @@ unused devices: &lt;none&gt;
</screen>
</para>
<para>I don't know if <filename>/proc/mdstat</filename> will reflect the status of a HOT SPARE. If you have set one up, you should be watching <filename>/var/log/messages</filename> for any disk failures. I'd like to get some logs of a disk failure, and <filename>/proc/mdstat</filename> from a system with a hot spare.</para>
<para>I don't know if <filename>/proc/mdstat</filename> will
reflect the status of a HOT SPARE. If you have set one up, you
should be watching <filename>/var/log/messages</filename> for any
disk failures. I'd like to get some logs of a disk failure, and
<filename>/proc/mdstat</filename> from a system with a hot
spare.</para>
</answer>
</qandaentry>
@ -240,8 +318,16 @@ unused devices: &lt;none&gt;
</question>
<answer>
<para>RAID generally doesn't mark a disk as bad unless it is, so you probably need a new disk. Most disks have a 3 year warranty, but some good SCSI hard drives may have a 5 year warranty. See if you can get the manufacturer to replace the failed disk for you.</para>
<para>When you get the new disk, power down the system, and install it, then partition the drive so that it has partitions the size of your missing RAID partitions. After you're finished partitioning the disk, use the command <command>raidhotadd</command> to put the new disk into the array and begin reconstruction.</para>
<para>RAID generally doesn't mark a disk as bad unless it is, so
you probably need a new disk. Most disks have a 3 year warranty,
but some good SCSI hard drives may have a 5 year warranty. See
if you can get the manufacturer to replace the failed disk for
you.</para> <para>When you get the new disk, power down the
system, and install it, then partition the drive so that it has
partitions the size of your missing RAID partitions. After
you're finished partitioning the disk, use the command
<command>raidhotadd</command> to put the new disk into the array
and begin reconstruction.</para>
</answer>
</qandaentry>
@ -249,11 +335,18 @@ unused devices: &lt;none&gt;
<qandaentry>
<question>
<para><command>dmesg</command> shows <quote>md: serializing resync, md4 has overlapping physical units with md5</quote>. What does this mean?</para>
<para><command>dmesg</command> shows <quote>md: serializing
resync, md4 has overlapping physical units with md5</quote>.
What does this mean?</para>
</question>
<answer>
<para>In that message <quote>physical units</quote> refers to disks, and not to blocks on the disks. Since there is more than 1 RAID array that needs resyncing on a disk, the RAID code is going to sync md4 first, and md5 second, to avoid excessive seeks (also called thrashing), which would drastically slow the resync process.</para>
<para>In that message <quote>physical units</quote> refers to
disks, and not to blocks on the disks. Since there is more than
1 RAID array that needs resyncing on a disk, the RAID code is
going to sync md4 first, and md5 second, to avoid excessive seeks
(also called thrashing), which would drastically slow the resync
process.</para>
</answer>
</qandaentry>