AW: recover short-time-power-failure of raid 5?

AW: recover short-time-power-failure of raid 5?

[Martin Bene]

Hi markus,

> I suggest that after assembling the array, you 'fsck' the filesystem
> on md0 just to make sure that the data is fine and then simply hot-add
> the third device:
>   mdadm /dev/md0 -a /dev/sdc
> 
> If fsck reports lots of error..... maybe try force the assmbly from a
> different pair of drives. e.g.
>    mdadm -A --force /dev/sda1 /dev/sdc2
> 
> and then do the fsck.

Oh, and if you try this: DON'T allow fsck to change/fix anything on the disks
if you want to later try a different combination - data corruption is pretty
much guaranteed if you allow any writes and then change to a different set of
disks.

Bye, Martin
PS: not sure what happens if you're using a journaling fs on the raid - I
think fsck replays the journal before checking, so trying out different
combinations of disk doesn't look like a viable option in that case?

Re: AW: recover short-time-power-failure of raid 5?

[Neil Brown]

On Monday November 25, martin.bene@icomedias.com wrote:
> PS: not sure what happens if you're using a journaling fs on the raid - I
> think fsck replays the journal before checking, so trying out different
> combinations of disk doesn't look like a viable option in that case?

With ext3, "fsck -n" doesn't replay the journal, but will report
errors that would be fixed by replaying the journal.  You would have
to ask yourself 'do these look like major errors, or just minor things
that the journal replay would fix'.

NeilBrown