Re: Failed RAID6

[NeilBrown <neilb@suse.de>]

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On Fri, 24 Feb 2012 11:56:39 -0600 (CST) Larry Owen <larryowen@cis.uab.edu>
wrote:

> We have a raid6 array with 3 "failed" discs.  However, smart 
> status for all drives is ok.  I'm also not seeing any io errors
> in my logs (except when the discs were initially dropped). I 
> also tried reading raw data from one of the failed drives, 
> using dd.  I was able to get data, still no io errors.
> 
> We're thinking about trying to re-add or assemble --force,
> in hopes of getting it up to recover some data (did I mention
> the users put important data on here knowing it was not backed
> up).
> 
> Our main concern is that we add the discs and the system start 
> rebuilding.  Any suggestions on how we should proceed?

Use assemble --force - this situation is exactly what it is for.

mdadm -S /dev/md0
mdadm -A --force /dev/md0

You might need to list all the component devices, depending on what is in
your mdadm.conf

NeilBrown


> 
> Thanks,
> Larry Owen
> 
> ################### MDADM OUTPUT ##############################
> 
> mdadm --detail /dev/md0 
> /dev/md0:
>         Version : 1.2
>   Creation Time : Tue Feb  1 16:25:03 2011
>      Raid Level : raid6
>   Used Dev Size : 1953512960 (1863.02 GiB 2000.40 GB)
>    Raid Devices : 22
>   Total Devices : 21
>     Persistence : Superblock is persistent
> 
>     Update Time : Wed Feb 22 23:42:11 2012
>           State : active, FAILED, Not Started
>  Active Devices : 19
> Working Devices : 21
>  Failed Devices : 0
>   Spare Devices : 2
> 
>          Layout : left-symmetric
>      Chunk Size : 512K
> 
>            Name : kddm-nas:0  (local to host kddm-nas)
>            UUID : 9fc31e38:7723974a:1f37af62:5a75ec91
>          Events : 5412
> 
>     Number   Major   Minor   RaidDevice State
>        0       8       16        0      active sync   /dev/sdb
>        1       8       32        1      active sync   /dev/sdc
>        2       8       48        2      active sync   /dev/sdd
>        3       8       64        3      active sync   /dev/sde
>        4       8       80        4      active sync   /dev/sdf
>        5       8       96        5      active sync   /dev/sdg
>        6       8      112        6      active sync   /dev/sdh
>        7       0        0        7      removed
>        8       8      144        8      active sync   /dev/sdj
>        9       8      160        9      active sync   /dev/sdk
>       10       8      176       10      active sync   /dev/sdl
>       11       0        0       11      removed
>       12       8      208       12      active sync   /dev/sdn
>       13       8      224       13      active sync   /dev/sdo
>       14       8      240       14      active sync   /dev/sdp
>       15       0        0       15      removed
>       16      65       16       16      active sync   /dev/sdr
>       17      65       32       17      active sync   /dev/sds
>       18      65       48       18      active sync   /dev/sdt
>       19      65       64       19      active sync   /dev/sdu
>       20      65       80       20      active sync   /dev/sdv
>       21      65       96       21      active sync   /dev/sdw
> 
>       22      65      112        -      spare   /dev/sdx
>       23      65      128        -      spare   /dev/sdy
> 
> 
> 
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