Bart Van Assche, on 03/02/2010 09:59 AM wrote:
On Mon, Mar 1, 2010 at 9:12 PM, Vladislav Bolkhovitin <[email protected]> wrote:
[ ... ]
It's good if my impression was wrong. But you've got suspiciously low IOPS
numbers. On your hardware you should have much more. Seems you experienced a
bottleneck on the initiator somewhere above the drivers level (fio? sg
engine? IRQs or context switches count?), so your results could be not
really related to the topic. Oprofile and lockstat output can shed more
light on this.
You didn't understand the purpose of the test. My goal was not to
achieve record IOPS numbers but to stress the SRP and iSER initiators
as much as possible. I choose the sg I/O engine in order to bypass the
block layer.
No, Bart, I understood your purpose very well. I'll illustrate my point
on example. Let's consider we want to compare a Ferrari and Toyota
Corolla cars. The only track we have to use has 60km/h speed limit, so
we used it strictly following the speed limit. Would we have a correct
comparison of the cars' capabilities, or would we compare only their
speedometers' mistakes? If Toyota's speedometer allows to stay more
closely to the limit, Toyota can win Ferrari. But would it win too on
180 km/h limit? Or without speed limit at all?
The same is in our topic. We can consider your experiment correct only
if the bottleneck is driver/hardware, which isn't likely to be.
Vlad
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