ZFS server has gone crazy slow

Andriy Gapon avg at FreeBSD.org
Sun Apr 12 11:57:44 UTC 2020


On 12/04/2020 14:54, Peter Eriksson wrote:
> 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.)

I think even earlier.  Before v26.

>> 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


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