qgroup scan causes system lockups and software crashes, disabling quotas disables size measurement of snapshots. Is there a way to make this work? about snapper

[aschnell]

You should be able to make snapper not doing quota rescans by having limits with no range (e.g. NUMBER_LIMIT=10 instead of 10-20) and using --disable-used-space with snapper ls. Likely not
setting QGROUP in the config have the same effect. But in the end disabling quota is simpler.

Unfortunately otherwise you are right.

[pallaswept]

You should be able to make snapper not doing quota rescans by having limits with no range (e.g. NUMBER_LIMIT=10 instead of 10-20) and using --disable-used-space with snapper ls. Likely not setting QGROUP in the config have the same effect. But in the end disabling quota is simpler.

Unfortunately otherwise you are right.

Thanks so much for the direct answer. Thanks especially for the tip about using fixed limits (not ranges), I'll give that a shot and see if it has a positive impact, but you have given me some hope :) OpenSUSE TW is using ranges by default, so that might part of my problem.

Most of the time the gqroup scans are a result of automated background processes, so I can't intervene by adding that parameter. At least now I know that I can try and fix my settings up, and if that fails, I need to make a decision between the lesser of the two evils, and should it come to that, I think I will just disable quotas for now.

I really appreciate your quick reply and your candor, you've taken a weight off my shoulders. Have a good one until next time!

[pallaswept]

For the record, indeed changing from ranges to fixed values, relieved the problems with constant qgroup scans locking up the system. However this simply uncovered similar behaviour from btrfs-cleaner and btrfs-transaction. Researching the problem, everywhere I read, said essentially the same thing - quotas don't behave well once you have a lot of snapshots. The Arch wiki literally begins its section on BTRFS quotas with a giant red warning to this effect, and then links to kernel documentation warning of the same. to quote the linux kernel's own documentation:

Combining quota with (too many) snapshots of subvolumes can cause performance problems, for example when deleting snapshots.

Finally I came across official documentation regarding the matter, on OpenSUSE at least - https://www.suse.com/support/kb/doc/?id=000020696 and the advice was to apply the workaround of disabling quotas. I've gone ahead and done that, unfortunately, as I can see their useful nature, but their performance penalty is beyond acceptable.

I don't believe they should be enabled on openSUSE by default when they are known to be broken.