Hi, I had a RAID5 double disk failure (40 megs or so bad sectors near middle of the second failed disk), bad news but I recovered what I was able to.
The RAID contained a dm-crypt physical volume which then contained four logical volumes. Two are EXT4 and two BTRFS, about 1TB in size each. The failure occurred while the volumes were online and in use, so in addition to what was unreadable, all pending writes to the device between the failure and when the problem was discovered were lost as well. The two ext4, fortunately, had some relatively minor corruption which was cleared up with a few rounds of fsck. The two btrfs are completely unhappy though and I do not know how to proceed, since btrfs problems are new to me. Any suggestions are welcome. Here is the basic picture of what is going on. # cat /etc/fstab # <file system> <mount point> <type> <options> <dump> <pass> #/dev/mapper/tr5ut-media /mnt/media btrfs defaults,compress=lzo,space_cache 0 2 /dev/mapper/tr5ut-media /mnt/media ext4 defaults 0 2 /dev/mapper/tr5ut-vicep--library /vicepa auto defaults,compress=lzo,space_cache 0 2 /dev/mapper/tr5ut-vicep--clones /vicepb auto defaults,compress=lzo,space_cache 0 2 You can see that btrfs device scan does not find anything, while btrfs-show finds one of the volumes and not the other. Fscking the found volume halts due to checksum and assertion errors, while fscking the other volume fails completely, I guess due to a missing 'superblock' type structure? seraph:~# btrfs device scan Scanning for Btrfs filesystems failed to read /dev/sr0 seraph:~# btrfs-show ** ** WARNING: this program is considered deprecated ** Please consider to switch to the btrfs utility ** failed to read /dev/sr0: No medium found Label: vicep-library uuid: 89b14d35-b31a-4fbe-a2d9-cb83cbcd3851 Total devices 1 FS bytes used 254.35GB devid 1 size 1.00TB used 299.04GB path /dev/dm-32 Btrfs Btrfs v0.19 seraph:~# btrfsck /dev/mapper/tr5ut-vicep--library checksum verify failed on 317874630656 wanted 8E19212D found FFFFFFA6 checksum verify failed on 317874630656 wanted 8E19212D found FFFFFFA6 checksum verify failed on 317874630656 wanted 491D9C1A found FFFFFFA6 checksum verify failed on 317874630656 wanted 8E19212D found FFFFFFA6 Csum didn't match btrfsck: root-tree.c:46: btrfs_find_last_root: Assertion `!(path->slots[0] == 0)' failed. Aborted seraph:~# btrfsck /dev/mapper/tr5ut-vicep--clones No valid Btrfs found on /dev/mapper/tr5ut-vicep--clones seraph:~# dpkg -l btrfs-tools Desired=Unknown/Install/Remove/Purge/Hold | Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend |/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad) ||/ Name Version Description +++-=============================================-=============================================-========================================================================================================== ii btrfs-tools 0.19+20111105-2 Checksumming Copy on Write Filesystem utilities -- Ryan C. Underwood, <neme...@icequake.net> -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html