Re: strangely uncorrectable errors with RAID-5

[Russell Coker <russell@coker.com.au>]

On Friday, 14 March 2025 23:27:51 AEDT Russell Coker wrote:
> Just to see if anything had changed I ran the same tests with RAID-5 data
> and metadata again with the Debian kernel 6.12.17-amd64 and this time got
> properly uncorrectable errors in less than a minute.  I don't know if the
> error happened faster and worse than before because of some kernel
> difference, luck, or some timing difference when running on different
> hardware.

I did it again but with RAID-5 data and RAID-1 metadata and it took a few 
hours this time but again got to an uncorrectable state.

[15653.298999] BTRFS warning (device vdc): checksum error at logical 
5157748736 on dev /dev/vdc, physical 1673199616: metadata leaf (level 0) in 
tree 5
[15653.299001] BTRFS error (device vdc): unable to fixup (regular) error at 
logical 5157748736 on dev /dev/vdc physical 1673199616
[15653.299002] BTRFS warning (device vdc): checksum error at logical 
5157748736 on dev /dev/vdc, physical 1673199616: metadata leaf (level 0) in 
tree 5
[15653.299003] BTRFS error (device vdc): unable to fixup (regular) error at 
logical 5157748736 on dev /dev/vdc physical 1673199616
[15653.299005] BTRFS warning (device vdc): checksum error at logical 
5157748736 on dev /dev/vdc, physical 1673199616: metadata leaf (level 0) in 
tree 5
[15653.299006] BTRFS error (device vdc): unable to fixup (regular) error at 
logical 5157748736 on dev /dev/vdc physical 1673199616
[15653.299007] BTRFS warning (device vdc): checksum error at logical 
5157748736 on dev /dev/vdc, physical 1673199616: metadata leaf (level 0) in 
tree 5
[15653.299009] BTRFS error (device vdc): unable to fixup (regular) error at 
logical 5157748736 on dev /dev/vdc physical 1673199616
[15653.299010] BTRFS warning (device vdc): checksum error at logical 
5157748736 on dev /dev/vdc, physical 1673199616: metadata leaf (level 0) in 
tree 5

Below is the script that broke it.

#!/bin/bash
set -e
while true ; do
  for DEV in c d e f ; do
    dd if=/dev/zero of=/dev/vd$DEV oseek=$((20+$RANDOM%3*1000)) bs=1024k 
count=1000
    sync
    btrfs scrub start -B /mnt
    sync
  done
  date
done

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