[Lustre-discuss] Quota performance

[Craig Tierney]

Mag Gam wrote:
> Thanks Andreas. We are planning to implement 250GB per user. Do you
> think there will be a performance degration?
> 

We put a requirement on our integrator to ensure that measured performance
was with quotas turned on.  We have seen enough other filesystems were
the performance penalty for enabling quotas was not acceptable.  The
vendor ran some performance tests (timing kernel compiles, iozone) with
quotas off and on.  From what I remember, the performance difference was
only a couple of percent.

Craig



> 
> On Wed, Sep 24, 2008 at 4:11 PM, Andreas Dilger <adilger at sun.com> wrote:
>> On Sep 24, 2008  06:11 -0400, Mag Gam wrote:
>>> I was wondering if we should implement quotas for our students but is
>>> there a downside such as performance? Previously, we implemented
>>> quotes using vxfs and we noticed a significant performance hit and the
>>> users were not happy. So, are there any downsides such as performance
>>> loss when using quotas?
>> There is defitely some performance overhead for quotas.  I don't have
>> a number offhand.  The actual performance overhead depends on how hard
>> you are pushing the network/filesystem already - if the IO rates aren't
>> extreme then the network quota overhead probably isn't too bad.
>>
>> The quota for Lustre is designed to be high performance, with some
>> sacrifice to the accuracy of the quota.  It isn't really designed to
>> handle tiny quotas (like 50MB/user), if that is your target.
>>
>> Cheers, Andreas
>> --
>> Andreas Dilger
>> Sr. Staff Engineer, Lustre Group
>> Sun Microsystems of Canada, Inc.
>>
>>
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-- 
Craig Tierney (craig.tierney at noaa.gov)