help with recover data from software raid 1

[Jeffrey Gray]

And as always, best practice would tell you that you should clone
before anything.  Grab another drive of equal or larger LBA and bit
for bit clone the drive.

On Mon, Aug 1, 2011 at 8:59 PM, Luis Paulo <luis.barbas at gmail.com> wrote:
> 2011/7/31 Franz Waldmüller <waldbauernbub at gmx.at>:
>> Hi,
>>
>> I want to recover files from a disk which has been part of a raid1 array. I
>> don't want to mount it degraded, as all operations must be read only.
>>
>> Can I mount the partiton of the disk as an ext4 filesystem (the raid was
>> formatted as ext4.)?
>>
>> Background:
>> In my server to harddisks are used in mirrored array to save all important
>> data.
>> /dev/sdb1 and /dev/sdc1
>>
>> today I created another md-device with the created partitions /dev/sdb2 and
>> /dev/sdc2. Unfortunately I didn't edit the /etc/mdadm/mdadm.conf file
>> properly.
>> When I rebooted the server I checked /proc/mdstat
>> and saw the following resync process:
>>
>> md1 : active raid1 sdc[1] sdb2[0]
>>      391382976 blocks [2/2] [UU]
>>      [>....................]  resync =  0.1% (745088/391382976)
>>
>> That is wrong, as the first device is sdc, but it should be sdc2.
>> I halted the server and now have to recover the files from /dev/sdb1.
>> /dev/sdc1 could have suffered damage from the resync process.
>>
>> I hope that you can help me with your advice.
>>
>> Franz
>
>
> I don't understand why you don't want to assemble the array as degraded.
>
> The way I'll recover the array will be clearing the super-block of
> /dev/sdc1, assemble the array as degraded with dev/sdb1 and then add
> /dev/sdc1 (using mdadm commands). At least this is the general idea, I
> may (and you must before trying it) look more carefully into it.
> After a resync, the array would be functional again.
>
> Regards
> Luis
>
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