[arch-general] Btrfs RAID1 corrupted after crash

[Leonardo Dagnino]

2014-04-13 17:23 GMT-03:00 Maximilian Bräutigam <m at xbra.de>:
> Dear all,
>
> unfortunately, I am very very deperate and I highly appreciate any help.
> One week ago, I move my entire system to btrfs to setup a RAID1. I
> created the RAID between device /dev/sdb and /dev/sdc with no
> partition table on normal HDDs. Everything was working smoothly until
> my computer crashed and at reboot I was not able to mount the device
> (my home dir) again and got the following messages:
>
> [  125.834802] BTRFS info (device sdc): disk space caching is enabled
> [  130.600101] BTRFS error (device sdc): block group 1268688879616 has
> wrong amount of free space
> [  130.600113] BTRFS error (device sdc): failed to load free space
> cache for block group 1268688879616
> [  130.751274] BTRFS critical (device sdc): corrupt leaf, slot offset
> bad: block=1268477591552,root=1, slot=137
> [  130.751659] BTRFS critical (device sdc): corrupt leaf, slot offset
> bad: block=1268477591552,root=1, slot=137
>
> So I cleared the cache with trying the mount option clear_cache, but
> it stayed problematic and I was not able to mount it:
>
> [  368.159594] BTRFS: error (device sdc) in __btrfs_free_extent:5755:
> errno=-5 IO failure
> [  368.159602] BTRFS: error (device sdc) in
> btrfs_run_delayed_refs:2713: errno=-5 IO failure
> [  368.165584] BTRFS warning (device sdc): Skipping commit of aborted
> transaction.
> [  368.165589] BTRFS: error (device sdc) in cleanup_transaction:1545:
> errno=-5 IO failure
> [  368.165787] BTRFS: error (device sdc) in open_ctree:2839: errno=-5
> IO failure (Failed to recover log tree)
> [  368.227161] BTRFS: open_ctree failed
>
> Now, if I tried to mount it manually with degraded option enabled:
>
> # mount -t btrfs -o degraded /dev/sdb /mnt/sonst/
> mount: wrong fs type, bad option, bad superblock on /dev/sdb,
>        missing codepage or helper program, or other error
>
>        In some cases useful info is found in syslog - try
>        dmesg | tail or so.
>
> Now I run btrfsck with repair option enabled but still I cannot mount it.
> Here you can find the dmesg and btrfsck outputs:
> dmesg: http://pastebin.com/zsaKQ0h1
> btrfsck: http://pastebin.com/xva6uJwT
>
> Please, help me! ;( Are there other options to investigate my RAID or
> to even temporarily mount it to get some data? What went wrong here?
> What can I do? Why is a simple crash making my RAID unusable? Can I
> use other tools for a recovery?
>
> Again, every help is highly appreciated.
> Best wishes,
> Max
> PS: Archlinux, linux-3.14-5, btrfs-progs-3.14-1

I don't really know a lot about RAID volumes, but shouldn't there be a
way to mount only one half of the array (only one of the partitions in
RAID)?
Also, if you recently updated anything that may be the cause of the
problem (I'd say the kernel), you may try to create a bootable USB
with the previous version of said packages to access or restore it.

Best regards,
-- 
Leonardo Dagnino