Re: RAID 5 array recovery - two drives errors in external enclosure

[Tim Bostrom <tbostrom@gmail.com>]

Is there any mdadm command that would have given any info or metadata
from the previous array?  I have almost 9 months of SSH logging on my
laptop that I use to manage the array.  Maybe there's some useful info
left in the log that might help.

-Tim

On Fri, Sep 18, 2009 at 1:07 AM, Robin Hill <robin@robinhill.me.uk> wrote:
> On Thu Sep 17, 2009 at 09:19:58PM -0700, Tim Bostrom wrote:
>
>> This seemed to work, though I'm still working through the permutations
>> of the drive letters.
>>
>> I noticed that mdadm think that partition sde1 is ext2 filesystem on
>> it.  See below:
>>
>> [root@tera tbostrom]# mdadm -C /dev/md0 -l 5 -n 5 -c 256 /dev/sdb1
>> /dev/sdd1 /dev/sdc1 /dev/sde1 missing
>> mdadm: /dev/sdb1 appears to be part of a raid array:
>>     level=raid5 devices=5 ctime=Thu Sep 17 21:13:21 2009
>> mdadm: /dev/sdd1 appears to be part of a raid array:
>>     level=raid5 devices=5 ctime=Thu Sep 17 21:13:21 2009
>> mdadm: /dev/sdc1 appears to be part of a raid array:
>>     level=raid5 devices=5 ctime=Thu Sep 17 21:13:21 2009
>> mdadm: /dev/sde1 appears to contain an ext2fs file system
>>     size=396408836K  mtime=Mon Sep 21 03:41:16 2026
>> mdadm: /dev/sde1 appears to be part of a raid array:
>>     level=raid5 devices=5 ctime=Thu Sep 17 21:13:21 2009
>> Continue creating array?
>>
>> What gives?  I tried popping sdf1 in there without creating the array
>> - just to see what would happen and it thinks that sdf1 has ext2 as
>> well.
>>
> That would suggest that sde1 is the first disk in the array (I think).
>
>> Still at a loss here.  I haven't worked through all the drive
>> permutations.  In the meantime, I'll try that.  Does it make sense to
>> try sdf1 in the permutation since the drive letters may have changed
>> since moving from the enclosure?  I thought I put them back in the
>> same order as the enclosure.
>>
> Definitely not - we know sdf1 has been re-written when you did the
> initial --create after moving the drives out of the enclosure.  This
> means it _definitely_ has invalid data on it.
>
> Unfortunately, without having the metadata information from the
> _original_ array _after_ it has been moved from the enclosure, there's
> no way of knowing what order the drives should be in.  I _think_ that
> sde1 will be the first disk (as it shows up as an ext2 filesystem), but
> you'll really have to try every possible combination of the 5 devices
> (the 4 partitions and "missing").  You may be best scripting this (or
> searching to see whether someone's already done that) - there's 120
> possible combinations to try.
>
> Cheers,
>    Robin
>
> --
>     ___
>    ( ' }     |       Robin Hill        <robin@robinhill.me.uk> |
>   / / )      | Little Jim says ....                            |
>  // !!       |      "He fallen in de water !!"                 |
>



-- 
-tim
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