On 2017年12月28日 09:46, Stirling Westrup wrote: > Here's my situation: I have a network file server containing a 12TB > BTRFS spread out over four devices (sda-sdd) which I am trying to > recover. I do have a backup, but it's about 3 months old, and while I > could certainly rebuild everything from that if I really had to, I > would far rather not have to rerip my latest DVDs. So, I am willing to > experiment if it might save me a few hundred hours of reconstruction. > I don't currently have another 12 TB of space anywhere for making a > scratch copy. > > A few days ago sdb developed hard errors and I can no longer mount the > filesystem. sdb is no longer even recognized as a valid btrfs drive. > However, when I ran ddrescue over the drive I managed to make a clone > (sdf) which contains all but 12K of the original drive. However, those > missing 12K are all in the various superblocks, so the cloned drive is > still unreadable. > > In the hopes that I was only missing a few bits of the superblocks, I > started out by dd-ing the first 4M of sdd into sdf in the hopes that > ddrescue would overwrite much of the superblocks, and the final bits > from sdd would make things usable. > > No such luck. I now have a drive sdf which claims to be identical to > sdd but which is a clone of sdb. In case it matters, sda and sdc are > each 4TB while sdb and sdd are each 2TB drives; sde is my boot drive > and sdf is a 2TB clone of sdb. > > What I need to do is to somehow patch sdf's primary superblock so it > contains the correct device number and UUID_SUB for sdb, so that I can > attempt some sort of recovery. Right now my linux is (understandably) > quite confused by the situation:
Did you tried "btrfs rescue super-recover"? Remember to use the devel branch from git, as there is a small bug prevent it report correct result. super-recover will try to use the backup superblock to recover the primary one. Thanks, Qu > > videon:~ # uname -a > Linux videon 4.4.103-18.41-default #1 SMP Wed Dec 13 14:06:33 UTC 2017 > (f66c68c) x86_64 x86_64 x86_64 GNU/Linux > > videon:~ # btrfs --version > btrfs-progs v4.5.3+20160729 > > videon:~ # btrfs fi show > Label: 'Storage' uuid: 33d2890d-f07d-4ba8-b1fc-7b4f14463b1f > Total devices 4 FS bytes used 10.69TiB > devid 1 size 1.82TiB used 1.82TiB path /dev/sdd > devid 3 size 3.64TiB used 3.54TiB path /dev/sdc > devid 4 size 3.64TiB used 3.54TiB path /dev/sda > *** Some devices missing > > Any suggestions on how to proceed would be appreciated. >
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