On 8/12/2013 3:43 AM, Wes wrote:

Stan Hoeppner <stan <at> hardwarefreak.com> writes:

quoted

~$ cat /sys/block/sda/queue/scheduler
[CFQ] noop deadline
Wes, yours will show CFQ probably as the default on RHEL/CentOS.  You'll
want deadline for best seek and all around performance.  So:
~$ echo deadline > /sys/block/sda/queue/scheduler
Add that to an init script or cron entry so it sets on every boot.
Barriers are not an issue with this test.

Thank you all. The issue is now closed.
RHEL5 was not doing cache flush right. It was only corrected in 2.6.32+
After removing O_SYNC from seekmark the results are now comparable.

Glad you got it figured out.

Actually it is hard to find a linux raw device random R/W benchmark tool and

FIO is good for raw IO benchmarking.  Can do file based IO as well.
Very flexible, but maybe a bit complicated for first time users.

seekmark being the most popular fails when comparing pre and post 2.6.32
systems (unless you remove O_SYNC).

Dunno about seekmark being the most popular.  I'd never heard of it
until this thread.  I'd have guessed FIO was most popular.  But then
again I don't get out much. ;)

-- 
Stan