Thanks for your answer!
On 27.05.2020 06:47, Zygo Blaxell wrote:
On Tue, May 26, 2020 at 04:44:25AM +0200, Michael Thomas wrote:
Hey,
I just wanted to ask if it's maybe possible to restore data from an old,
failed, raid5 btrfs fs. There are some files on it which I lost lately and
before I format the drives I wanted to give it another shot after some (6?)
years.
I'm not sure what I tried before, but there are 3 drives there, was 4 before
but 1 died (and this seems to be the problem of the disaster).
I tried to add 1 new, but that didn't worked.
So, there are 3 devices and as far as I understand, there are still no good
tools to rescue data from them, are they? btrfs restore and other seems only
compatible with 1 drive.
But maybe someone can give me a hint what I can try before giving up.
If I try to mount:
mount -o degraded,subvol=data,ro,device=/dev/mapper/sdb,device=/dev/mapper/sdd,device=/dev/mapper/sde
/dev/mapper/sde /mnt/test
dmesg give this errors:
BTRFS warning (device dm-4): suspicious: generation < chunk_root_generation:
176279 < 176413
BTRFS info (device dm-4): allowing degraded mounts
BTRFS info (device dm-4): disk space caching is enabled
BTRFS warning (device dm-4): devid 4 uuid
16490fb1-df5e-4c81-9c07-4f799d0fc132 is missing
BTRFS warning (device dm-4): devid 5 uuid
36436209-c0d4-4a5e-9176-d44c94cb4b39 is missing
That's 2 missing disks. Assuming that is accurate (were there 5 in
total?), it is not likely recoverable with raid5.
No, there was a raid5 with 4 disks, 1 failed and I tried to replace it
with another one. It failed at the placement process, so that may the
reason why there are 2 missing disks?
raid5 tolerates only one disk failure--two or more failures, and you'll
only be able to get 64K contiguous chunks of data without any idea
what files they belong to.
If the messages are _not_ accurate, you might have a corrupted superblock
on one of the disks that is making 'btrfs dev scan' fail. If you can
identify which disk that is, 'btrfs rescue super-recover' might help
(though it sounds like you already tried and it didn't).
BTRFS critical (device dm-4): corrupt leaf: block=1095416938496 slot=151
extent bytenr=1095389085696 len=16384 invalid generation, have 176581 expect
(0, 176280]
BTRFS error (device dm-4): block=1095416938496 read time tree block
corruption detected
You may have more luck with kernel 4.19, which is a LTS kernel without
the read time tree block corruption detector; however, that won't be able
to read past the corrupted tree block, it will only let you mount the
filesystem to try to salvage other data.
Tried it with the last 4.19 kernel, even there it's not mounted :(
[ 230.267404] BTRFS warning (device dm-2): suspicious: generation <
chunk_root_generation: 176279 < 176413
[ 230.267407] BTRFS info (device dm-2): allowing degraded mounts
[ 230.267412] BTRFS info (device dm-2): disk space caching is enabled
[ 230.269808] BTRFS warning (device dm-2): devid 4 uuid
16490fb1-df5e-4c81-9c07-4f799d0fc132 is missing
[ 230.269810] BTRFS warning (device dm-2): devid 5 uuid
36436209-c0d4-4a5e-9176-d44c94cb4b39 is missing
[ 230.282425] BTRFS error (device dm-2): parent transid verify failed
on 1095416938496 wanted 176276 found 176581
[ 230.282792] BTRFS error (device dm-2): parent transid verify failed
on 1095416938496 wanted 176276 found 176581
[ 230.282797] BTRFS warning (device dm-2): failed to read root
(objectid=4): -5
[ 230.283441] BTRFS error (device dm-2): open_ctree failed
Any advices to help with this?
A btrfs restore or anything like this for raid5 would be really great =/
BTRFS critical (device dm-4): corrupt leaf: block=1095416938496 slot=151
extent bytenr=1095389085696 len=16384 invalid generation, have 176581 expect
(0, 176280]
BTRFS error (device dm-4): block=1095416938496 read time tree block
corruption detected
BTRFS warning (device dm-4): failed to read root (objectid=4): -5
BTRFS error (device dm-4): open_ctree failed
(usebackuproot changed nothing and super-recover prints "All supers are
valid, no need to recover")
Do you have any hint, advice to get (some of) this data back?
Best,
Michael
