[linux-lvm] Re: IO scheduler, queue depth, nr_requests
Kevin P. Fleming
kpfleming at backtobasicsmgmt.com
Mon Feb 16 19:32:00 UTC 2004
Jens Axboe wrote:
> On Mon, Feb 16 2004, Miquel van Smoorenburg wrote:
>> as you might have seen from the linux-kernel mailinglist
>>I have been testing for months now with a fileserver set up to
>>use XFS over LVM2 on a 3ware RAID5 controller.
I too have been fighting lower-than-expected performance with this
identical combination, other than using a P4 2.8GHz instead of 3.0GHz,
and 1GB RAM instead of 2GB. My 3ware 8506-8 has six Seagate Barracuda
SATA drives behind it, which are very fast on their own :-) Try as I
might, with the 2.6 kernel I have not been able to generate a bonnie++
or iozone run that provided performance better than a single disk, even
with the 3ware card in JBOD, RAID-0 or RAID-1 mode. I had been
conversing with 3ware about it, but to no real effect given than they
don't support 2.6 yet.
>>By fiddling about today I just found that changing
>>/sys/block/sda/queue/nr_requests from 128 to something above
>>the queue depth of the 3ware controller (256 doesn't work,
>>384 and up do) also fixes the problem.
I will try this as well this evening and report my results.
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