BTRFS " the free space cache file (nnnnn) is invalid"

[Ancan]

Hi all,

I've got an annoying issue with BTRFS where accessing the file system sometimes stalls, snapshot transfers takes forever/never completes and for two nights in a row, a frozen Unraid-box in the morning.

 

In the syslog, the only sign of anything abnormal is multiple "kernel: BTRFS info (device md6): the free space cache file (nnnnnnnn) is invalid, skip it". It's always the same disk, which is the disk I use to store backup-snapshots of VM's/containers which are transferred from the cache-drive nightly.  There's no hardware related timeouts or similar which I'd suspect if there was a hardware issue.

 

I assume it's some filesystem-issue, but "btrfs check" shows no errors, "scrub" finds no errors and mounting the disk with "clear_cache" option makes no difference.

 

I'm currently evacuating the disk so I can reformat it but wanted to ask if anyone has any idea what the problem might be and if so, if it's possible to repair.

 

Edit: On 6.8.2 now, but have been on the beta that had the 5.x kernel until today.

 

Edited January 31, 2020 by Ancan
Added version info.

[JorgeB]

That's relatively normal and usually no reason for concern, that's why it appears as "info", not "warning" or "error", and it usually goes way by itself, doubt that's the reason for the reported issues.

[Ancan]

33 minutes ago, johnnie.black said:

That's relatively normal and usually no reason for concern, that's why it appears as "info", not "warning" or "error", and it usually goes way by itself, doubt that's the reason for the reported issues.

Thanks! Then I'll ignore these in the future. and hope it goes away after a reformat.

[JorgeB]

It should, re: snapshots, try to keep as few snapshots as possible, the more snapshots you have the slower the filesystem will become, low single double digits are recommended.

[Ancan]

1 minute ago, johnnie.black said:

It should, re: snapshots, try to keep as few snapshots as possible, the more snapshots you have the slower the filesystem will become, low single digits are recommended.

I'm keeping about 20 (four weekly and a bunch of daily). Perhaps I'm expecting too much to imitate the setup I've done on the NetApp's at work, but expected a bit more from btrfs is that is the case.

[JorgeB]

18 minutes ago, johnnie.black said:

low single digits are recommended.

20 should be fine, I meant to say low double digits.