Re: Error mounting multi-device fs after restart

[Diwaker Gupta <diwaker@maginatics.com>]

Help, anyone? Sorry for the quick repost, but there was some important
data on that filesystem that I don't have a backup for. I'd really
appreciate any pointers that can help recover the data.

Searching through the archives, it seems others have faced similar
issues due to sudden power outages. AFAIK we did not have any power
outage.

I've run badblocks on all of the 10 drives and three of them had a few
bad blocks. I'm inclined to rule out bad disks as the root cause. In
any case, isn't this exactly the kind of situation btrfs should
protect users against?

A 'btrfsck' aborts on all of the drives. I've tried running it with
'-s 1' as well as '-s 2' with no success. Does that mean that none of
the drives have any copy of the superblock intact?

Diwaker

On Mon, Feb 7, 2011 at 11:46 AM, Diwaker Gupta <diwaker@maginatics.com> wrote:
> Hello,
>
> We have 10 1-TB drives hosting a multi-device btrfs filesystem,
> configured with raid1+0 for both data and metadata. After some package
> upgrades over the weekend I restarted the system and it did not come
> back up afterwards. I booted using a rescue disk and ran btrfsck (next
> branch from Chris's git repository). Unfortunately btrfsck aborts on
> every single drive with errors like this:
>
> parent transid verify failed on 12050980864 wanted 377535 found 128327
> parent transid verify failed on 12074557440 wanted 422817 found 126691
> parent transid verify failed on 12057542656 wanted 422786 found 126395
> parent transid verify failed on 12075556864 wanted 423004 found 126691
> bad block 12095545344
> parent transid verify failed on 12079190016 wanted 422826 found 105147
> leaf parent key incorrect 12097544192
> bad block 12097544192
>
> I'm running 10.04 Ubuntu Lucid with the lts-backport x86_64 kernel:
> 2.6.35-23-server
>
> Attempting to mount the filesystem blocks indefinitely, with
> /var/log/messages getting filled with the 'parent transid verify'
> errors.
>
> IIUC the 'btrfs-select-super' utility is not really helpful in our
> case. At this point, my only priority is to somehow rescue the data
> from the filesystem. I'd really appreciate if someone on the list
> could help me out.
>
> I'm happy to provide any other information required. Please CC me on
> replies as I'm not subscribed to the list.
>
> Thanks,
> Diwaker
>