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

From: Magnus Hagander <magnus(at)hagander(dot)net>
To: Scott Otis <scott(dot)otis(at)intand(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Ivan Voras <ivoras(at)freebsd(dot)org>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Seeking performance advice and explanation for high I/O on 8.3
Date: 2009-09-04 08:18:57
Message-ID: 9837222c0909040118r6095db73yd6fe6c64fae73534@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
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/

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Subject: slow query : very simple delete, 100% cpu, nearly no disk activity
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