blog/data/2012-02-14-raid-disk.txt

   1 Title: How to figure out which RAID disk to replace when it fail
   2 Tags: english, raid
   3 Date: 2012-02-14 21:25
   4
   5 <p>Once in a while my home server have disk problems.  Thanks to Linux
   6 Software RAID, I have not lost data yet (but
   7 <a href="http://comments.gmane.org/gmane.linux.raid/34532">I was
   8 close</a> this summer :).  But once a disk is starting to behave
   9 funny, a practical problem present itself.  How to get from the Linux
  10 device name (like /dev/sdd) to something that can be used to identify
  11 the disk when the computer is turned off?  In my case I have SATA
  12 disks with a unique ID printed on the label.  All I need is a way to
  13 figure out how to query the disk to get the ID out.</p>
  14
  15 <p>After fumbling a bit, I
  16 <a href="http://www.cyberciti.biz/faq/linux-getting-scsi-ide-harddisk-information/">found
  17 that hdparm -I</a> will report the disk serial number, which is
  18 printed on the disk label.  The following (almost) one-liner can be
  19 used to look up the ID of all the failed disks:</p>
  20
  21 <blockquote><pre>
  22 for d in $(cat /proc/mdstat |grep '(F)'|tr ' ' "\n"|grep '(F)'|cut -d\[ -f1|sort -u);
  23 do
  24     printf "Failed disk $d: "
  25     hdparm -I /dev/$d |grep 'Serial Num'
  26 done
  27 </blockquote></pre>
  28
  29 <p>Putting it here to make sure I do not have to search for it the
  30 next time, and in case other find it useful.</p>
  31
  32 <p>At the moment I have two failing disk. :(</p>
  33
  34 <blockquote><pre>
  35 Failed disk sdd1:       Serial Number:      WD-WCASJ1860823
  36 Failed disk sdd2:       Serial Number:      WD-WCASJ1860823
  37 Failed disk sde2:       Serial Number:      WD-WCASJ1840589
  38 </blockquote></pre>
  39
  40 <p>The last time I had failing disks, I added the serial number on
  41 labels I printed and stuck on the short sides of each disk, to be able
  42 to figure out which disk to take out of the box without having to
  43 remove each disk to look at the physical vendor label.  The vendor
  44 label is at the top of the disk, which is hidden when the disks are
  45 mounted inside my box.</p>
  46
  47 <p>I really wish the check_linux_raid Nagios plugin for checking Linux
  48 Software RAID in the
  49 <a href="http://packages.qa.debian.org/n/nagios-plugins.html">nagios-plugins-standard</a>
  50 debian package would look up this value automatically, as it would
  51 make the plugin a lot more useful when my disks fail.  At the moment
  52 it only report a failure when there are no more spares left (it really
  53 should warn as soon as a disk is failing), and it do not tell me which
  54 disk(s) is failing when the RAID is running short on disks.</p>