Mikael Abrahamsson <swmike <at> swm.pp.se> writes:

On Thu, 25 Jul 2013, Wes wrote:

quoted

Why raid10 driver from Centos 6 has a 300% slower random write performance
(random read stays the same) than Centos 5?

Please share your ideas.

...
Does seekmark use barriers to assure that data has actually been written? 
In that case it could be that 2.6.18 has different behaviour from 2.6.32 
when it comes to barriers and that explains the speed difference.

Yes, the kernels are as you stated.
I used seekmark from http://learnitwithme.com/?page_id=267 
and I am not so savvy to say if it uses barriers or not.
Linear write speed (dd) is the same on centos5 and centos6. 
Just the random write (seekmark) got horrible.

I found a way to disable barriers but for filesystems only. 
As I am testing block device not sure if barriers have something to it.