unable to mount btrfs

[Adel Ahmed]

I had a raid 5 array of 3 disks using btrfs (raid provided by btrfs)
one of the disks was damaged and I replaced the disk via :
btrfs device add /dev/sdc /media/raid/
btrfs device delete missing /media/raid/

which forced a rebalance accross the disks, after which the FS was fine

one reboot later:
[11152.188020] BTRFS info (device sdb): enabling auto defrag
[11152.188028] BTRFS info (device sdb): disk space caching is enabled
[11152.189762] BTRFS: failed to read chunk tree on sdb
[11152.196224] BTRFS: open_ctree failed

pc ~ # mount -a
mount: wrong fs type, bad option, bad superblock on /dev/sde,
missing codepage or helper program, or other error

In some cases useful info is found in syslog - try
dmesg | tail or so.


the OS started by commenting out that line in fstab, I've uncommented that line afterwards
LABEL="raid" /media/raid btrfs compress=lzo,noatime,autodefrag

[massimo]

Does it mount when adding degraded to mount options?
_________________
Hello 911? How are you?

[Adel Ahmed]

no

I've tried btrfs rescue chunk-recover /dev/sdb -v

got plenty of :
Chunk: start = 1461400371200, len = 2147483648, type = 81, num_stripes = 3
Stripes list:
[ 0] Stripe: devid = 4, offset = 299575017472
[ 1] Stripe: devid = 3, offset = 119194779648
[ 2] Stripe: devid = 1, offset = 119214702592
Chunk: start = 1463547854848, len = 2147483648, type = 81, num_stripes = 3
Stripes list:
[ 0] Stripe: devid = 4, offset = 300648759296
[ 1] Stripe: devid = 3, offset = 118121037824
[ 2] Stripe: devid = 1, offset = 118140960768
Chunk: start = 1465695338496, len = 2147483648, type = 81, num_stripes = 3
Stripes list:
[ 0] Stripe: devid = 4, offset = 301722501120
[ 1] Stripe: devid = 3, offset = 117047296000
[ 2] Stripe: devid = 1, offset = 117067218944


and plenty of:
Device extent: devid = 4, start = 413391650816, len = 1073741824, chunk offset = 1689033637888
Device extent: devid = 4, start = 414465392640, len = 1073741824, chunk offset = 1691181121536
Device extent: devid = 4, start = 415539134464, len = 1073741824, chunk offset = 1693328605184


but ended with:
Floating point exception

[ATpwwu]

just restore from backup

[Adel Ahmed]

I have no backup, I was hoping raid 5 would protect me from all this

[ct85711]

raid systems are not a replacement for a backup. A raid is only there to provide some redundancy in case of a hardware failure. Raid 0 is an exception in that it provides no redundancy either. Most times, the other raids may protect you from 1-2 device failures (depending on raid level, and number of devices) and could still end up causing you to loose everything (when rebuilding the raid, causing more drives to die)

[Adel Ahmed]

well is there anyway to recover the raid?
if not, any way to recover the data?

[massimo]

Did you try to run btrfs check --repair /dev/sdb? If all fails try to get help at the btrfs mailing list.
_________________
Hello 911? How are you?

[Adel Ahmed]

enabling repair mode
warning, device 4 is missing
checksum verify failed on 1699771072512 found 35F941C0 wanted D11AFC76
checksum verify failed on 1699771072512 found 35F941C0 wanted D11AFC76
bytenr mismatch, want=1699771072512, have=65536
Couldn't read chunk root
Couldn't open file system

[Adel Ahmed]

any way I can at least recover the data on the device?

pc ~ # btrfs restore /dev/sdb /media/hdd/ -o
warning devid 2 not found already
parent transid verify failed on 1699771121664 wanted 270069 found 270891
parent transid verify failed on 1699771121664 wanted 270069 found 270891
checksum verify failed on 1699771121664 found 267F2F7E wanted C29C92C8
parent transid verify failed on 1699771121664 wanted 270069 found 270891
Ignoring transid failure
Error mapping block -2
Error copying data for /media/hdd/downloads/The.Butterfly.Effect.2004.DC.1080p.BluRay.AAC.x264-tomcat12[ETRG]/Torrent Downloaded From ExtraTorrent.cc.txt
Error searching /media/hdd/downloads/The.Butterfly.Effect.2004.DC.1080p.BluRay.AAC.x264-tomcat12[ETRG]/Torrent Downloaded From ExtraTorrent.cc.txt
Error searching /media/hdd/downloads/The.Butterfly.Effect.2004.DC.1080p.BluRay.AAC.x264-tomcat12[ETRG]/Torrent Downloaded From ExtraTorrent.cc.txt