Jim,
I tried as you suggested and my performance dropped by 50%. I went from
a 32 TPS to 16. Oh well.
Steve
On Wed, 2006-08-09 at 16:05 -0500, Jim C. Nasby wrote:
> 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
> > >
> > >
>