Hello!
A degraded BTRFS RAID 1 from one 3TB SATA HDD of my former workstation is not
mountable.
Debian 4.8 kernel + btrfs-tools 4.7.3.
A btrfs restore seems to work well enough, so on one hand there is no
urgency. But on the other hand I want to repurpose the harddisk and I
think I want to do it next weekend. So if you want me to gather some
debug data, please speak up quickly. Thank you.
AFAIR I have been able to mount the filesystems in degraded mode, but
this may have been on the other SATA HDD that I already wiped with shred
command.
I have this:
merkaba:~> btrfs fi sh
[…]
warning, device 2 is missing
warning, device 2 is missing
warning, device 2 is missing
Label: 'debian' uuid: […]
Total devices 2 FS bytes used 20.10GiB
devid 1 size 50.00GiB used 29.03GiB path
/dev/mapper/satafp1-debian
*** Some devices missing
Label: 'daten' uuid: […]
Total devices 2 FS bytes used 135.02GiB
devid 1 size 1.00TiB used 142.06GiB path
/dev/mapper/satafp1-daten
*** Some devices missing
Label: 'backup' uuid: […]
Total devices 2 FS bytes used 88.38GiB
devid 1 size 1.00TiB used 93.06GiB path
/dev/mapper/satafp1-backup
*** Some devices missing
But none of these filesystems seem to be mountable. Here some attempts:
merkaba:~#130> LANG=C mount -o degraded /dev/satafp1/backup /mnt/zeit
mount: wrong fs type, bad option, bad superblock on
/dev/mapper/satafp1-daten,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so.
merkaba:~> dmesg | tail -5
[ 2945.155943] BTRFS info (device dm-13): allowing degraded mounts
[ 2945.155953] BTRFS info (device dm-13): disk space caching is enabled
[ 2945.155957] BTRFS info (device dm-13): has skinny extents
[ 2945.611236] BTRFS warning (device dm-13): missing devices (1) exceeds
the limit (0), writeable mount is not allowed
[ 2945.646719] BTRFS: open_ctree failed
merkaba:~> LANG=C mount -o usebackuproot /dev/satafp1/daten /mnt/zeit
mount: wrong fs type, bad option, bad superblock on
/dev/mapper/satafp1-daten,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so.
merkaba:~#32> dmesg | tail -5
[ 5739.051433] BTRFS info (device dm-12): trying to use backup root at
mount time
[ 5739.051441] BTRFS info (device dm-12): disk space caching is enabled
[ 5739.051444] BTRFS info (device dm-12): has skinny extents
[ 5739.103153] BTRFS error (device dm-12): failed to read chunk tree: -5
[ 5739.130304] BTRFS: open_ctree failed
merkaba:~> LANG=C mount -o degraded,usebackuproot /dev/satafp1/daten
/mnt/zeit
mount: wrong fs type, bad option, bad superblock on
/dev/mapper/satafp1-daten,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so.
merkaba:~#32> dmesg | tail -5
[ 5801.704202] BTRFS info (device dm-12): trying to use backup root at
mount time
[ 5801.704206] BTRFS info (device dm-12): disk space caching is enabled
[ 5801.704208] BTRFS info (device dm-12): has skinny extents
[ 5803.928059] BTRFS warning (device dm-12): missing devices (1) exceeds
the limit (0), writeable mount is not allowed
[ 5804.064638] BTRFS: open_ctree failed
`btrfs check` reports:
merkaba:~#32> btrfs check /dev/satafp1/backup
warning, device 2 is missing
Checking filesystem on /dev/satafp1/backup
UUID: 01cf0493-476f-42e8-8905-61ef205313db
checking extents
checking free space cache
failed to load free space cache for block group 58003030016
failed to load free space cache for block group 60150513664
failed to load free space cache for block group 62297997312
[…]
checking fs roots
^C
I aborted it at this time as I wanted to try clear_cache mount option
after seeing this. I can redo this thing after btrfs restore completed.
merkaba:~> mount -o degraded,clear_cache /dev/satafp1/backup /mnt/zeit
mount: Falscher Dateisystemtyp, ungültige Optionen, der
Superblock von /dev/mapper/satafp1-backup ist beschädigt, fehlende
Kodierungsseite oder ein anderer Fehler
Manchmal liefert das Systemprotokoll wertvolle Informationen –
versuchen Sie dmesg | tail oder ähnlich
merkaba:~#32> dmesg | tail -6
[ 3080.120687] BTRFS info (device dm-13): allowing degraded mounts
[ 3080.120699] BTRFS info (device dm-13): force clearing of disk cache
[ 3080.120703] BTRFS info (device dm-13): disk space caching is enabled
[ 3080.120706] BTRFS info (device dm-13): has skinny extents
[ 3080.150957] BTRFS warning (device dm-13): missing devices (1) exceeds
the limit (0), writeable mount is not allowed
[ 3080.195941] BTRFS: open_ctree failed
merkaba:~> mount -o degraded,clear_cache,usebackuproot /dev/satafp1/backup
/mnt/zeit
mount: Falscher Dateisystemtyp, ungültige Optionen, der
Superblock von /dev/mapper/satafp1-backup ist beschädigt, fehlende
Kodierungsseite oder ein anderer Fehler
Manchmal liefert das Systemprotokoll wertvolle Informationen –
versuchen Sie dmesg | tail oder ähnlich
merkaba:~> dmesg | tail -7
[ 3173.784713] BTRFS info (device dm-13): allowing degraded mounts
[ 3173.784728] BTRFS info (device dm-13): force clearing of disk cache
[ 3173.784737] BTRFS info (device dm-13): trying to use backup root at
mount time
[ 3173.784742] BTRFS info (device dm-13): disk space caching is enabled
[ 3173.784746] BTRFS info (device dm-13): has skinny extents
[ 3173.816983] BTRFS warning (device dm-13): missing devices (1) exceeds
the limit (0), writeable mount is not allowed
[ 3173.865199] BTRFS: open_ctree failed
I aborted repairing after this assert:
merkaba:~#130> btrfs check --repair /dev/satafp1/backup &| stdbuf -oL tee
btrfs-check-repair-satafp1-backup.log
enabling repair mode
warning, device 2 is missing
Checking filesystem on /dev/satafp1/backup
UUID: 01cf0493-476f-42e8-8905-61ef205313db
checking extents
Unable to find block group for 0
extent-tree.c:289: find_search_start: Assertion `1` failed.
btrfs[0x43e418]
btrfs(btrfs_reserve_extent+0x5c9)[0x4425df]
btrfs(btrfs_alloc_free_block+0x63)[0x44297c]
btrfs(__btrfs_cow_block+0xfc)[0x436636]
btrfs(btrfs_cow_block+0x8b)[0x436bd8]
btrfs[0x43ad82]
btrfs(btrfs_commit_transaction+0xb8)[0x43c5dc]
btrfs[0x4268b4]
btrfs(cmd_check+0x1111)[0x427d6d]
btrfs(main+0x12f)[0x40a341]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf1)[0x7fb2e6bec2b1]
btrfs(_start+0x2a)[0x40a37a]
merkaba:~#130> btrfs --version
btrfs-progs v4.7.3
(Honestly I think asserts like this need to be gone from btrfs-tools for good)
About this I only found this unanswered mailing list post:
btrfs-convert: Unable to find block group for 0
Date: Fri, 24 Jun 2016 11:09:27 +0200
https://www.spinics.net/lists/linux-btrfs/msg56478.html
Out of curiosity I tried:
merkaba:~#1> btrfs rescue zero-log //dev/satafp1/daten
warning, device 2 is missing
Clearing log on //dev/satafp1/daten, previous log_root 0, level 0
Unable to find block group for 0
extent-tree.c:289: find_search_start: Assertion `1` failed.
btrfs[0x43e418]
btrfs(btrfs_reserve_extent+0x5c9)[0x4425df]
btrfs(btrfs_alloc_free_block+0x63)[0x44297c]
btrfs(__btrfs_cow_block+0xfc)[0x436636]
btrfs(btrfs_cow_block+0x8b)[0x436bd8]
btrfs[0x43ad82]
btrfs(btrfs_commit_transaction+0xb8)[0x43c5dc]
btrfs[0x42c0d4]
btrfs(main+0x12f)[0x40a341]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf1)[0x7fb2f16a82b1]
btrfs(_start+0x2a)[0x40a37a]
(I didn´t expect much as this is an issue that AFAIK does not happen
easily anymore, but I also thought it could not do much harm)
Superblocks themselves seem to be sane:
merkaba:~#1> btrfs rescue super-recover //dev/satafp1/daten
All supers are valid, no need to recover
So "btrfs restore" it is:
merkaba:[…]> btrfs restore -mxs /dev/satafp1/daten daten-restore
This prints out a ton of:
Trying another mirror
Trying another mirror
But it actually works. Somewhat, I now just got
Trying another mirror
We seem to be looping a lot on
daten-restore/[…]/virtualbox-4.1.18-dfsg/out/lib/vboxsoap.a, do you want to
keep going on ? (y/N/a):
after about 35 GiB of data restored. I answered no to this one and now it is
at about 53 GiB already. I just got another one of these, but also not
concerning a file I actually need.
Thanks,
--
Martin Steigerwald | Trainer
teamix GmbH
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90449 Nürnberg
Tel.: +49 911 30999 55 | Fax: +49 911 30999 99
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