| From: | "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com> |
|---|---|
| To: | Joost Kraaijeveld <J(dot)Kraaijeveld(at)Askesis(dot)nl> |
| Cc: | "Pgsql-Performance (E-mail)" <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Can anyone explain this pgbench results? |
| Date: | 2006-03-07 19:09:34 |
| Message-ID: | 20060307190933.GY82989@pervasive.com |
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| Lists: | pgsql-performance |
On Mon, Mar 06, 2006 at 04:29:49PM +0100, Joost Kraaijeveld wrote:
> I was expecting a low(ish) score the first run (because the tables are not loaded in the cache yet), followed by continues high(ish) scores, but not an alternating pattern. I also did not expect so much difference, given the hardware I have (Dual Opteron, 4GB memory , 3Ware SATA RAID5 with 5 disks, seerate swap and pg_log disks).
On a side-note:
RAID5 and databases generally don't mix well.
Most people find that pg_xlog will live happily with the OS; it's the
data files that need the most bandwidth.
If you start swapping, performance will tank to the point that it's
unlikely that swap being on seperate disks will help at all. Better off
to just keep it with the OS and use the disks for the database tables.
Speaking of 'disks', what's your exact layout? Do you have a 5 drive
raid5 for the OS and the database, 1 drive for swap and 1 drive for
pg_xlog?
--
Jim C. Nasby, Sr. Engineering Consultant jnasby(at)pervasive(dot)com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
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