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* how to restore a raid5 with 1 disk destroyed and 1 kicked out?
@ 2009-04-07 14:02 "Jörg Habenicht"
  2009-04-07 14:30 ` Followup: " "Jörg Habenicht"
  0 siblings, 1 reply; 2+ messages in thread
From: "Jörg Habenicht" @ 2009-04-07 14:02 UTC (permalink / raw)
  To: linux-raid

Hello list, hello Neil,

I hope you may help me with this one:

During a RAID5 synchronisation with one faulty disk my server crashed and left my RAID in an unsynced state. I'd like to get the content from the array back to freshen my last backup (4 months ago) and then build the array anew.

The array consists of 6 disks, right now 1 is dead (hw failure) and one is "out of sync". I assume the latter is just marked out of sync without being so.(*)


In http://www.mail-archive.com/linux-raid@vger.kernel.org/msg08909.html and http://www.mail-archive.com/linux-raid@vger.kernel.org/msg06332.html you suggested to recreate the array with --assume-clean.
In http://www.mail-archive.com/linux-raid@vger.kernel.org/msg08162.html you advised not to use --assume-clean for RAID5, it may very well break.
Is it ok to use --assume-clean on a degraded array (5 out of 6, RAID5)?


Would it be better to recreate the array without --assume-clean? (E.g. like "mdadm --create /dev/md0 disk1 disk2 disk3 missing disk5 disk6")

Just out of interest: What is the difference between the two commands?

I think /deb/sdb1 is marked "out of sync" without being so. Is "--assume-clean" used exactly for this case?


Thank you in advance for any advice or help
cu
Jörg



(*)
/dev/sdd1 dropped dead
/dev/sdb1 is marked 'out of sync', but I think the content on the disk is in sync with the array


 Now the dirty details:

~ # mdadm -S /dev/md0
mdadm: stopped /dev/md0

~ # mdadm --assemble --force /dev/md0  --run --verbose  /dev/sdb1 /dev/hda1 /dev/sdc1  /dev/sde1  /dev/sdf1
mdadm: looking for devices for /dev/md0
mdadm: /dev/sdb1 is identified as a member of /dev/md0, slot 6.
mdadm: /dev/hda1 is identified as a member of /dev/md0, slot 1.
mdadm: /dev/sdc1 is identified as a member of /dev/md0, slot 2.
mdadm: /dev/sde1 is identified as a member of /dev/md0, slot 3.
mdadm: /dev/sdf1 is identified as a member of /dev/md0, slot 5.
mdadm: no uptodate device for slot 0 of /dev/md0
mdadm: added /dev/sdc1 to /dev/md0 as 2
mdadm: added /dev/sde1 to /dev/md0 as 3
mdadm: no uptodate device for slot 4 of /dev/md0
mdadm: added /dev/sdf1 to /dev/md0 as 5
mdadm: added /dev/sdb1 to /dev/md0 as 6
mdadm: added /dev/hda1 to /dev/md0 as 1
mdadm: failed to RUN_ARRAY /dev/md0: Input/output error
mdadm: Not enough devices to start the array.

~ # cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4] [raid1]
md0 : inactive hda1[1] sdf1[5] sde1[3] sdc1[2]
      976791680 blocks

~ # mdadm -D /dev/md0
/dev/md0:
        Version : 00.90.03
  Creation Time : Mon Apr  3 12:35:48 2006
     Raid Level : raid5
  Used Dev Size : 244195904 (232.88 GiB 250.06 GB)
   Raid Devices : 6
  Total Devices : 4
Preferred Minor : 0
    Persistence : Superblock is persistent

    Update Time : Tue Apr  7 12:02:58 2009
          State : active, degraded, Not Started
 Active Devices : 4
Working Devices : 4
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 64K

           UUID : b72d31b8:f6bbac3d:c1c586ef:bb458af6
         Events : 0.3088065

    Number   Major   Minor   RaidDevice State
       0       0        0        0      removed
       1       3        1        1      active sync   /dev/hda1
       2       8       33        2      active sync   /dev/sdc1
       3       8       65        3      active sync   /dev/sde1
       4       0        0        4      removed
       5       8       81        5      active sync   /dev/sdf1

~ # mdadm -IR /dev/sdb1
mdadm: /dev/sdb1 attached to /dev/md0, not enough to start (4).

~ # cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4] [raid1]
md0 : inactive sdb1[0] hda1[1] sdf1[5] sde1[3] sdc1[2]
      1220987584 blocks

~ # mdadm -D /dev/md0
(.....)
    Number   Major   Minor   RaidDevice State
       0       8       17        0      spare rebuilding   /dev/sdb1
       1       3        1        1      active sync   /dev/hda1
       2       8       33        2      active sync   /dev/sdc1
       3       8       65        3      active sync   /dev/sde1
       4       0        0        4      removed
       5       8       81        5      active sync   /dev/sdf1



I already tried
- "mdadm --assemble /dev/md0 /dev/sdb1 /dev/hda1 /dev/sdc1 /dev/sde1  /dev/sdf1"
- "mdadm --assemble --force /dev/md0 /dev/sdb1 /dev/hda1 /dev/sdc1  /dev/sde1  /dev/sdf1"



-- 
cu,
Joerg

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2009-04-07 14:02 how to restore a raid5 with 1 disk destroyed and 1 kicked out? "Jörg Habenicht"
2009-04-07 14:30 ` Followup: " "Jörg Habenicht"

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