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Re: High load average with PostgreSQL 7.4.2 on

From: "Scott Marlowe" <smarlowe(at)qwest(dot)net>
To: eleven(at)ludojad(dot)itpp(dot)pl
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: High load average with PostgreSQL 7.4.2 on
Date: 2004-06-29 22:36:55
Message-ID: 1088548615.12350.44.camel@localhost.localdomain (view raw or flat)
Thread:
Lists: pgsql-performance
On Tue, 2004-06-29 at 09:55, eleven(at)ludojad(dot)itpp(dot)pl wrote:
> Hello,
> 
> I'm using PostgreSQL 7.4.2 (package from backports.org) 
> on a Debian (woody) box. The machine is IBM eServer 345
> with two 2.8 Xeon CPUs, it has 1024MB of RAM and
> two 15k RPM SCSI disks running in hardware RAID1, which
> is provided by the onboard LSI Logic controller (LSI53C1030).
> 
> The database consists of two rather large tables 
> (currently about 15 million rows in one table
> and about 5 million in the other one). Both tables
> have 5 indexes (4 btree/1 hash). 
> Application running on the server INSERTs a lot of 
> stuff to the tables (which is not the target use of
> the DB, it'll add data periodically, about
> 300 rows per 10 minutes). Queries (SELECTs) run perfectly
> fine on the database, thanks to the indexes we have
> here probably. 
> 
> Performance issue, I'm experiencing here, is somewhat
> weird - server gets high average load (from 5 up to 15,
> 8 on average). Standard performance monitoring
> utilities (like top) show that CPUs are not loaded 
> (below 20%, often near zero). 

Anytime you have high load but low CPU utilization, you usually have an
I/O bound system.

Ad disks to your RAID (big RAID 5 or RAID 1+0) and make sure you have
battery backed cache set to write back.  also, put as memory as you can
in the machine.  Jumping up to 2 Gigs may help quite a bit as well.


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