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List:       zfs-discuss
Subject:    Re: [zfs-discuss] ZFS (and quota)
From:       Neil Perrin <Neil.Perrin () Sun ! COM>
Date:       2007-09-27 22:40:42
Message-ID: 46FC316A.8010004 () Sun ! COM
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Roch - PAE wrote:
> Pawel Jakub Dawidek writes:
>  > I'm CCing zfs-discuss@opensolaris.org, as this doesn't look like
>  > FreeBSD-specific problem.
>  > 
>  > It looks there is a problem with block allocation(?) when we are near
>  > quota limit. tank/foo dataset has quota set to 10m:
>  > 
>  > Without quota:
>  > 
>  > 	FreeBSD:
>  > 	# dd if=/dev/zero of=/tank/test bs=512 count=20480
>  > 	time: 0.7s
>  > 
>  > 	Solaris:
>  > 	# dd if=/dev/zero of=/tank/test bs=512 count=20480
>  > 	time: 4.5s
>  > 
>  > With quota:
>  > 
>  > 	FreeBSD:
>  > 	# dd if=/dev/zero of=/tank/foo/test bs=512 count=20480
>  > 	dd: /tank/foo/test: Disc quota exceeded
>  > 	time: 306.5s
>  > 
>  > 	Solaris:
>  > 	# dd if=/dev/zero of=/tank/foo/test bs=512 count=20480
>  > 	write: Disc quota exceeded
>  > 	time: 602.7s
>  > 
>  > CPU is almost entirely idle, but disk activity seems to be high.
>  > 
> 
> 
> Yes, as we are near quota limit, each transaction group
> will accept a small amount as to not overshoot the limit.
> 
> I don't know if we have the optimal strategy yet.
> 
> -r

Aside from the quota perf issue, has any analysis been done as to
why FreeBSD is over 6X faster than Solaris without quotas?
Do other perf tests show a similar disparity?
Is there a difference in dd itself?
I assume that it was identical hardware and pool config.

Thanks: Neil.
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