Hello Chris,

thanks for your reply.

 >Remove the discard mount option for this file system and see if that
 >fixes the problem. Run it for a week or two, or until you're certain
 >the problem is still happening (or certain it's gone). Some drives
 >just can't handle sync discards, they become really slow and hang,
 >just like you're reporting.

 In fstab, this option is not set:
 /dev/disk/by-label/DataPool1            /srv/dev-disk-by-label-DataPool1
         btrfs   noatime,defaults,nofail 0 2

You have more than one btrfs file system.
grep btrfs
/dev/sdc2 on /srv/dev-disk-by-label-DockerImages type btrfs (rw,noatime,ssd,discard,space_cache,subvolid=5,subvol=/) /dev/sdd2 on /srv/dev-disk-by-label-Daten type btrfs (rw,relatime,ssd,space_cache,subvolid=5,subvol=/) /dev/sda1 on /srv/dev-disk-by-label-DataPool1 type btrfs (rw,noatime,space_cache,subvolid=5,subvol=/)

You can see, that for sdc2 and sdd2, "ssd" is in the mount options. For sdc2 discard is present. I have not added this myelf. But it is in fstab.
In fact, I got confused in my previous mail:
sdc is an ssd and not the drive that I was experiencing problems with (well: The system was slow when accessing sda1. I cannot exclude, that this was caused by sdc2.

I'm suggesting not using
discard on any of them to try and narrow down the problem.  Something
is turning on discards for sdc2, find it and don't use it for a while.
Will do.

 How do I deactivate discard then?
 These drives are spinning disks. I thought that discard is only relevant
 for SSDs?

It's relevant for thin provisioning and sparse files too. But if sdc2
is a HDD then the sync discard message isn't related to the problem,
but also makes me wonder why something is enabling sync discards on a
See above. It was my mistake, thinking it sdc2 was the spinning disc.

Anway I think you're on the right track to try 5.11.11 and if you
experience a hang again, use sysrq+w and that will dump the blocked
task trace into dmesg. Also include a description of the workload at
the time of the hang, and recent commands issued.
Ok, will do.


Chris Murphy

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