[zfs-discuss] ZFS (and quota)

[Robert Milkowski]

Hello Neil,

Thursday, September 27, 2007, 11:40:42 PM, you wrote:


NP> Roch - PAE wrote:
>> Pawel Jakub Dawidek writes:
>>  > I'm CCing zfs-discuss at 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

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

Good question.
It should have been cached on Solaris so it should definitely be below
1s range.

-- 
Best regards,
 Robert                            mailto:rmilkowski at task.gda.pl
                                       http://milek.blogspot.com