[CentOS] Write performance with 3ware 9550

Bowie Bailey
Thu, 12 Oct 2006 23:58:35 -0000

chrism at imntv.com wrote:
> 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-
> --Random-
>                     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block--
> --Seeks--
> 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
> 42 625.8
>
> 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.

With NCQ off, I get these results:

Version  1.03       ------Sequential Output------ --Sequential Input-
--Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block--
--Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec
%CP
Second          50G           20853   8 41899  11           192713  23 116.9
1

Write performance increased by 2M/s and read performance decreased by 2M/s.

What tweaks have you applied so far?  I would expect a 4-drive array
to be slower than an 8-drive array, but not this much!

--
Bowie