I've read through other I read through other posts and tried a bunch of different things but I am unable to mount my 4 disk cache pool

I've tried to attach the diagnostic but I can't figure it out

Here it is

plexmart-diagnostics-20260312-1856.zip

Mar 12 18:40:21 PlexMart kernel: BTRFS error (device sdq1): parent transid verify failed on logical 9917928243200 mirror 1 wanted 835404 found 835380

Mar 12 18:40:21 PlexMart kernel: BTRFS error (device sdq1): parent transid verify failed on logical 9917928243200 mirror 2 wanted 835404 found 835380

There were some writes lost to the pool, this is typically a device or controller firmware issue, i.e., it lied regarding write barriers.

This error is typically fatal, meaning the pool will need to be recreated, there are some recovery options below. btrfs restore is the one that has a better chance of working in this case, but try the other ones first:

https://forums.unraid.net/topic/46802-faq-for-unraid-v6/page/2/#findComment-543490

thank you. step 1 of mounting it RO appears to allow me to read SOME stuff.

I am copying everything from /temp to the array so I can rebuild the cache.

when I try to du -h --max-depth=1 /temp I get input/output error on 2 files and 2 VM folders.

Is it worth doing anything to repair those errors in order to not lose those 2 VMs?

2 hours ago, JorgeB said:

Mar 12 18:40:21 PlexMart kernel: BTRFS error (device sdq1): parent transid verify failed on logical 9917928243200 mirror 1 wanted 835404 found 835380

Mar 12 18:40:21 PlexMart kernel: BTRFS error (device sdq1): parent transid verify failed on logical 9917928243200 mirror 2 wanted 835404 found 835380

There were some writes lost to the pool, this is typically a device or controller firmware issue, i.e., it lied regarding write barriers.

This error is typically fatal, meaning the pool will need to be recreated, there are some recovery options below. btrfs restore is the one that has a better chance of working in this case, but try the other ones first:

https://forums.unraid.net/topic/46802-faq-for-unraid-v6/page/2/#findComment-543490

1 hour ago, elmetal said:

when I try to du -h --max-depth=1 /temp I get input/output error on 2 files and 2 VM folders.

They may be corrupt, you could try btrfs restore on those, it will skip any corrupt files, of course; they will still be corrupt, but depending on how much, it could still work or allow some recovery.

3 hours ago, JorgeB said:

They may be corrupt, you could try btrfs restore on those, it will skip any corrupt files, of course; they will still be corrupt, but depending on how much, it could still work or allow some recovery.

I copied what I could via btrfs restore etc.

Then I tried to do the --repair portion and got this as a result:


enabling repair mode WARNING: Do not use --repair unless you are advised to do so by a developer or an experienced user, and then only after having accepted that no fsck can successfully repair all types of filesystem corruption. E.g. some software or hardware bugs can fatally damage a volume. The operation will start in 10 seconds. Use Ctrl-C to stop it. 10 9 8 7 6 5 4 3 2 1parent transid verify failed on 9917928243200 wanted 835404 found 835380 parent transid verify failed on 9917928243200 wanted 835404 found 835380 parent transid verify failed on 9917928243200 wanted 835404 found 835380 Ignoring transid failure parent transid verify failed on 9917928259584 wanted 835404 found 835380 parent transid verify failed on 9917928259584 wanted 835404 found 835380 parent transid verify failed on 9917928259584 wanted 835404 found 835380 Ignoring transid failure ERROR: child eb corrupted: parent bytenr=9917925277696 item=23 parent level=2 child bytenr=9917928259584 child level=0 ERROR: failed to read block groups: Input/output error ERROR: cannot open file system Starting repair. Opening filesystem to check...

Like mentioned, this type of error is typically fatal, if you recovered what you can, you may need to reformat the pool.

btrfs check --repair --tree-root 9917919625216 /dev/sdX1

mount -o ro,usebackuproot /dev/sdq1 /mnt/recovery

Allowed me to remount it as rw, and allowed me to scrub for errors, it's all working now