Re: How to recover from btrfs scrub errors? (uncorrectable errors, checksum error at logical)

["Otto Kekäläinen" <otto@seravo.fi>]

I never got a reply to this thread, but I am not replying to myself in
case somebody has the same issue and is reading the archive:

The problem went away after:
- deleted all snapshots as they seemed to slow down btrfs I/O so much
that simple commands like rm and rsync were unusable
- replaced the disk that had the corrupted file (just in case -
smartctl did not indicate any disk failures) with btrfs replace
- rsynced files from another location to this filesystem so that the
corrupted files got overwritten

Now btrfs scrub does not find any corruption anymore and the
filesystem I/O speed is usable, though still slower than what it used
to be in the past.

ma 15. lokak. 2018 klo 10.50 Otto Kekäläinen (otto@seravo.fi) kirjoitti:
>
> Hello!
>
> I am trying to figure out how to recover from errors detected by btrfs scrub.
>
> Scrub status reports:
>
> scrub status for 4f4479d5-648a-45b9-bcbf-978c766aeb41
>         scrub started at Mon Oct 15 10:02:28 2018, running for 00:35:39
>         total bytes scrubbed: 791.15GiB with 18 errors
>         error details: csum=18
>         corrected errors: 0, uncorrectable errors: 18, unverified errors: 0
>
> Kernel log contains lines like
>
>   BTRFS warning (device dm-8): checksum error at logical 7351706472448 on dev
>   /dev/mapper/disk6tb, sector 61412648, root 12725, inode 152358265,
> offset 483328:
>   path resolving failed with ret=-2
>
> I've tried so far:
> - deleting the files (when path is visible)
> - overwriting the files with new data
> - changed disk (with btrfs replace)
>
> The checksum errors however persist.
> How do I get rid of them?
>
>
> The files are logs and other non-vital information. I am fine by
> deleting the corrupted files. It is OK to recover so that I loose a
> few gigabytes of data, but not the entire filesystem.
>
> Setup is a multi-disk btrfs filesystem, data single, metadata RAID-1
> Mounted with:
>
> /dev/mapper/wdc3td on /data type btrfs
> (rw,noatime,compress=lzo,space_cache,subvolid=5,subvol=/)
>
> I've read lots of online sources on the topic but none of these help
> me on how to recover from the current state:
>
> https://btrfs.wiki.kernel.org/index.php/Btrfsck
> http://marc.merlins.org/perso/btrfs/post_2014-03-19_Btrfs-Tips_-Btrfs-Scrub-and-Btrfs-Filesystem-Repair.html
> https://wiki.archlinux.org/index.php/Identify_damaged_files#Find_damaged_files



-- 
Otto Kekäläinen
CEO
Seravo
+358 44 566 2204

Follow me at @ottokekalainen