Re: Seeking performance advice and explanation for high I/O on 8.3

So is there anything I can do in 8.3 to help this? I have tried setting ' track_activities', 'track_counts' and 'autovacuum' to 'off' (which has reduced CPU and I/O a bit) - but the stats collector process is still using up a good deal of CPU and I/O - is there any way to turn stats collecting completely off?

Scott Otis
CIO / Lead Developer
Intand
www.intand.com

-----Original Message-----
From: Magnus Hagander [mailto:magnus(at)hagander(dot)net]
Sent: Friday, September 04, 2009 1:19 AM
To: Scott Otis
Cc: Robert Haas; Ivan Voras; pgsql-performance(at)postgresql(dot)org
Subject: Re: [PERFORM] Seeking performance advice and explanation for high I/O on 8.3

On Fri, Sep 4, 2009 at 08:54, Scott Otis<scott(dot)otis(at)intand(dot)com> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com>:
>
>> Do you by any chance have a bazillion databases in this cluster?  Can
>> you do these?
>
>> select sum(1) from pg_database;
>
> 1555

Note that there are two features in 8.4 specifically designed to deal with the situation where you have lots of databases and/or lots of tables (depending on how many tables you have in each database, this would definitely qualify). They both deal with the "pgstats temp file too large generating i/o issue".

First, it will only write the file when it's actually necessary - 8.3 and earlier will always write it.

Second, you will have the ability to move the location of the file to a different filesystem - specifically intended so that you can move it off to a ramdrive.

Could be worth investigating an upgrade for this issue alone. The fact that you don't have to struggle with tuning the FSM in 8.4 is another thing that makes life a *lot* easier in this kind of installations.

--
Magnus Hagander
Me: http://www.hagander.net/
Work: http://www.redpill-linpro.com/