Followup: how to restore a raid5 with 1 disk destroyed and 1 kicked out?

["\"Jörg Habenicht\"" <j.habenicht@gmx.de>]

http://www.mail-archive.com/linux-raid@vger.kernel.org/msg07640.html suggests sending the event count:

The event count of the devices is
/dev/hda1: 0.3088065
/dev/sdb1: 0.3088063 * (out of sync)
/dev/sdc1: 0.3088065
/dev/sdd1: 0.3088062 ** (dropped dead)
/dev/sde1: 0.3088065
/dev/sdf1: 0.3088065


cu
Jörg

-------- Original-Nachricht --------
> Datum: Tue, 07 Apr 2009 16:02:25 +0200
> Von: "Jörg Habenicht" <j.habenicht@gmx.de>
> An: linux-raid@vger.kernel.org
> Betreff: how to restore a raid5 with 1 disk destroyed and 1 kicked out?

> 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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> 
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-- 
cu,
Joerg

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