[CentOS] Write performance with 3ware 9550

Thu Oct 12 21:59:04 UTC 2006
chrism at imntv.com <chrism at imntv.com>

Bowie Bailey wrote:
> Joshua Baker-LePain wrote:
>> On Thu, 12 Oct 2006 at 4:22pm, Bowie Bailey wrote
>>> I have two identical servers.  The only difference is that the first
>>> one has Maxtor 250G drives and the second one has Seagate 320G
>>> drives. 
>>> OS: CentOS-4.4 (fully patched)
>>> CPU: dual Opteron 280
>>> Memory: 16GB
>>> Raid card: 3ware 9550Sx-8LP
>>> Raid volume: 4-disk Raid 5 with NCQ and Write Cache enabled
>>> On the first server I have decent performance.  Nothing spectacular,
>>> but good enough.  The second one has about 1/3 the write speed.  I
>>> can't find any difference between the systems.  Both of them have
>>> the same stripe size, both have ext3 filesystems, both have write
>>> caching and NCQ turned on.  I have already increased the read ahead
>>> setting to 16384 on both servers.
>> Turn off NCQ.  Last I knew, this was still 3ware's recommendation.
> I can try that, but when I tested on the first server, I found that
> disabling NCQ increased the read performance by 10M/s and decreased
> the write performance by 10M/s.  Maybe I'll get different results from
> the Seagate drives.

Here's what I'm getting from a dual Opteron 275 box, Centos 4.4-64bit, 
2gb RAM and an 8 drive array of 750gig Seagates:

Version  1.03       ------Sequential Output------ --Sequential Input- 
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- 
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  
/sec %CP
localhost.locald 4G           248901  96 138957  40           308874  42 

I've been applying all the various tricks that came up during the last 
couple of threads.  Turning NCQ off definitely made a big difference for me.