Re: IOPS higher than expected on randwrite, direct=1 tests

[Jens Axboe <jaxboe@fusionio.com>]

On 2010-11-10 20:52, Sebastian Kayser wrote:
> * John Cagle <jcagle@gmail.com> wrote:
>> If the disk is 2TB, then your 100GB test is only using 5% of it-- thus
>> your observed IOPS will be a lot better than expected due to
>> short-stroking.  Right?
> 
> I don't know. The inital 80 IOPS (observed over about 2 full minutes)
> made me believe that 100GB would have covered a high enough percentage
> to at least eliminate track-to-track seeks. Are short-stroked seeks also
> that much faster compared to average seek times? And where would the
> steady increase in IOPS during the test come from?
> 
> But you are definitly right when it comes to the test setup. I just
> started a test with size=1800g. Looking foward to what that will show.

If you have the full device, you could just test on that instead of
using a filesystem and file. Just to get more 'raw' performance.

-- 
Jens Axboe