ZFS server has gone crazy slow

[Peter Eriksson]

Hmm. By “ancient” pool version - are you thinking of the one used during FreeBSD 11.0-11.1 days? That was what we were using at the time when we tested “zfs destroy -r foo at bar” vs “zfs destroy -rd foo at bar” and found that “-d” was much quicker.

(We’re now at 11.3 and 12.1 and that whole snapshot cleaning script is completely rewritten and uses a custom “zfs” binary instead that can look at custom user properties to decided which snapshots to delete and not and is much more efficient in general.)

- Peter


> Note, however, that unless you have a very ancient pool version destroying a
> snapshot means that the snapshot object is removed and all blocks belonging to
> the snapshot are queued for freeing.  Their actual freeing is done
> asynchronously ("in background") and can be spread over multiple TXG periods.
> That's done regardless of whether -d was used.
> 
> -- 
> Andriy Gapon