Arch Linux

alanaktion

Member

Registered: 2016-03-04

Posts: 2

Website

RAID1 Btrfs filesystem fails to mount

I have a Btrfs filesystem using 6 partitionless disks in RAID1 that's failing to mount. I've tried the common recommended safe check options, but I haven't gotten the disk to mount at all, even with -o ro,recovery. If necessary, I can try to use the recovery to another filesystem, but I have around 18 TB of data on the filesystem that won't mount, so I'd like to avoid that if there's some other way of recovering it.

Based on my understanding of how RAID1 works with Btrfs, I would expect a single disk failure to not prevent the volume from mounting entirely, but I'm only seeing one disk with errors according to dmesg output:

[  534.519437] BTRFS warning (device sdd): 'recovery' is deprecated, use 'usebackuproot' instead
[  534.519441] BTRFS info (device sdd): trying to use backup root at mount time
[  534.519443] BTRFS info (device sdd): disk space caching is enabled
[  534.519446] BTRFS info (device sdd): has skinny extents
[  536.306194] BTRFS info (device sdd): bdev /dev/sdc errs: wr 23038942, rd 22208378, flush 1, corrupt 29486730, gen 2933
[  556.126928] BTRFS critical (device sdd): corrupt leaf: root=2 block=25540634836992 slot=45, unexpected item end, have 13882 expect 13898
[  556.134767] BTRFS critical (device sdd): corrupt leaf: root=2 block=25540634836992 slot=45, unexpected item end, have 13882 expect 13898
[  556.150278] BTRFS critical (device sdd): corrupt leaf: root=2 block=25540634836992 slot=45, unexpected item end, have 13882 expect 13898
[  556.150310] BTRFS error (device sdd): failed to read block groups: -5
[  556.216418] BTRFS error (device sdd): open_ctree failed

If helpful, here is some more-verbose lsblk output:

NAME   TYPE   SIZE FSTYPE MOUNTPOINT UUID
sda    disk 111.8G                   
├─sda1 part   1.9M                   
└─sda2 part 111.8G ext4   /          c598dfdf-d6e7-47d3-888a-10f5f53fa338
sdb    disk   7.3T btrfs             8f26ae2d-84b5-47d7-8f19-64b0ef5a481b
sdc    disk   7.3T btrfs             8f26ae2d-84b5-47d7-8f19-64b0ef5a481b
sdd    disk   7.3T btrfs             8f26ae2d-84b5-47d7-8f19-64b0ef5a481b
sde    disk   7.3T btrfs             8f26ae2d-84b5-47d7-8f19-64b0ef5a481b
sdf    disk   2.7T btrfs             8f26ae2d-84b5-47d7-8f19-64b0ef5a481b
sdh    disk   2.7T btrfs             8f26ae2d-84b5-47d7-8f19-64b0ef5a481b

My main system partition on sda mounts fine and is usable to work with the btrfs filesystem that's having issues.

Running btrfs check /dev/sdb exits with this:

Opening filesystem to check...
Incorrect offsets 13898 13882
ERROR: cannot open file system

I'm not sure what the best approach from here is, so any advice would be great. I'm reasonably familiar with btrfs, but haven't run into a situation like this before, and the documentation, both on the Arch Wiki and elsewhere, are very vague about things, with a lot of warnings about potentially making the problem worse, so I've avoided doing anything that didn't seem safe until I understand the problem better.

edacval

Member

From: .LT

Registered: 2008-10-23

Posts: 91

Re: RAID1 Btrfs filesystem fails to mount

https://bbs.archlinux.org/viewtopic.php … 2#p1820642