ReadyNAS 214, Meldung btrfs_sync_log+8e0

jimjonas​ -

I've looked at your logs.  

I am not seeing any disk errors for the disks you have installed now.  I think the resync that was in progress when you captured the logs was triggered by the system crash.

But there are a lot of BTRFS errors in kernel.log.  Some are:

Aug 06 19:34:25 NAS-NETGEAR-4 kernel: BTRFS error (device md127): bdev /dev/md127 errs: wr 28898, rd 4651, flush 0, corrupt 0, gen 0
Aug 06 19:34:31 NAS-NETGEAR-4 kernel: BTRFS error (device md127): bdev /dev/md127 errs: wr 28899, rd 4651, flush 0, corrupt 0, gen 0
Aug 06 19:37:34 NAS-NETGEAR-4 kernel: BTRFS error (device md127): bdev /dev/md127 errs: wr 28900, rd 4651, flush 0, corrupt 0, gen 0

I can't see what is causing these errors, but I am thinking they might be file system corruption resulting from the errors with the failed Ironwolf drive you replaced in March.

Repairing BTRFS errors is sometimes possible, but it is quite risky.  The tools are focused on fixing the file system itself, not on preserving your data.  I think the best approach is to back up all your data, and then create a new data volume.  Then re-create your shares, and restore the files from the backup.