[ZFS] refquota is very slow !

[Ben RUBSON]

> On 07 Sep 2016, at 11:38, Miroslav Lachman <000.fbsd at quip.cz> wrote:
> 
> Ben RUBSON wrote on 09/07/2016 10:44:
>> 
>> OK !
>> Well, Juergen you put me on the right way.
>> I investigated further and further and found that refquota slowness is not due to the number of files but to the remaining free space.
>> Let me explain this.
> 
> I don't have a bookmark so I can't send you a direct link but it was mentioned before. refquota is similar to full pool in this case, so if you are close to or over 80% full, you will notice this slowdown.
> You can try to search the web for details.

I found this interesting post from Matthew Ahrens :
http://marc.info/?l=freebsd-fs&m=137184901423584

However it does not explain the (huge) performance difference between quota and refquota.

I did not found many more interesting things.

> On 03 Sep 2016, at 16:59, Bram Vandoren <bram.vandoren at kuleuven.be> wrote:
> 
> I think the userquota property works without any problem though.

Yes you're right, Matthew Ahrens also indicates that userquota should not impact performance :
http://www.archivum.info/zfs-discuss@opensolaris.org/2010-08/00218/Re-(zfs-discuss)-ZFS-Group-Quotas.html
(which I also tested and can confirm)

Ben