Date: Wed, 9 Aug 2006 16:05:40 -0500
From: "Jim C. Nasby" <jnasby@pervasive.com>
To: Steve Poe <steve.poe@gmail.com>
Cc: Luke Lonergan <LLonergan@greenplum.com>, Alex Turner <armtuk@gmail.com>,
	pgsql-performance@postgresql.org
Subject: Re: Postgresql Performance on an HP DL385 and
Message-ID: <20060809210539.GR40481@pervasive.com>
References: <3E37B936B592014B978C4415F90D662D03FFEF6E@MI8NYCMAIL06.Mi8.com>
	<721b21dc0608082245u6ee62e7dg522ff18e4d72683@mail.gmail.com>
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On Tue, Aug 08, 2006 at 10:45:07PM -0700, Steve Poe wrote:
> Luke,
> 
> I thought so. In my test, I tried to be fair/equal since my Sun box has two
> 4-disc arrays each on their own channel. So, I just used one of them which
> should be a little slower than the 6-disc with 192MB cache.
> 
> Incidently, the two internal SCSI drives, which are on the 6i adapter,
> generated a TPS of 18.
 
You should try putting pg_xlog on the 6 drive array with the data. My
(limited) experience with such a config is that on a good controller
with writeback caching enabled it won't hurt you, and if the internal
drives aren't caching writes it'll probably help you a lot.

> I thought this server would impressive from notes I've read in the group.
> This is why I thought I might be doing something wrong. I stumped which way
> to take this. There is no obvious fault but something isn't right.
> 
> Steve
> 
> On 8/8/06, Luke Lonergan <LLonergan@greenplum.com> wrote:
> >
> >Steve,
> >
> >> Sun box with 4-disc array (4GB RAM. 4 167GB 10K SCSI RAID10
> >> LSI MegaRAID 128MB). This is after 8 runs.
> >>
> >> dbserver-dual-opteron-centos,08/08/06,Tuesday,20,us,12,2,5
> >> dbserver-dual-opteron-centos,08/08/06,Tuesday,20,sy,59,50,53
> >> dbserver-dual-opteron-centos,08/08/06,Tuesday,20,wa,1,0,0
> >> dbserver-dual-opteron-centos,08/08/06,Tuesday,20,id,45,26,38
> >>
> >> Average TPS is 75
> >>
> >> HP box with 8GB RAM. six disc array RAID10 on SmartArray 642
> >> with 192MB RAM. After 8 runs, I see:
> >>
> >> intown-vetstar-amd64,08/09/06,Tuesday,23,us,31,0,3
> >> intown-vetstar-amd64,08/09/06,Tuesday,23,sy,16,0,1
> >> intown-vetstar-amd64,08/09/06,Tuesday,23,wa,99,6,50
> >> intown-vetstar-amd64,08/09/06,Tuesday,23,id,78,0,42
> >>
> >> Average TPS is 31.
> >
> >Note that the I/O wait (wa) on the HP box high, low and average are all
> >*much* higher than on the Sun box.  The average I/O wait was 50% of one
> >CPU, which is huge.  By comparison there was virtually no I/O wait on
> >the Sun machine.
> >
> >This is indicating that your HP machine is indeed I/O bound and
> >furthermore is tying up a PG process waiting for the disk to return.
> >
> >- Luke
> >
> >

-- 
Jim C. Nasby, Sr. Engineering Consultant      jnasby@pervasive.com
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461