Date: Fri, 17 Jun 2011 11:51:43 -0700 (PDT)
From: Shianmiin <Shianmiin@gmail.com>
To: pgsql-admin@postgresql.org
Message-ID: <1308336703621-4499692.post@n5.nabble.com>
In-Reply-To: <1174.1305990672@sss.pgh.pa.us>
References: <4DD6D9A6.1010101@emolecules.com>
	<BANLkTikJ6xn-pKRhRA1HGiNotQt7N=1QDQ@mail.gmail.com>
	<4DD6FC11.4000706@emolecules.com> <1174.1305990672@sss.pgh.pa.us>
Subject: Re: Who is causing all this i/o?
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Tom Lane-2 wrote:
> 
> What's not apparent however is why the stats collector is writing disk
> so much.  8.4 does have the logic change to not write stats out unless
> something is asking to see them.  So either it's really pre-8.4, or you
> have a monitoring task that is constantly asking to see stats.
> 

We have a PostgreSQL 9.0.4 on CentOs for performance testing and we are
seeing the similar issue.
we have a "crazy" setup it has 1 database with 1000 identical schemas. There
are occasional I/O write storm
of over 100 MB/sec without any disk reads, and it could last for a couple of
minutes when the schemas/data are aggressively populated by pg_restore. All
the io writes seem to be on pgstat.tmp.

The I/O write storm seemed to be trigger by Vacuum.

The way we get around that is to point stats_temp_directory to ram disk
which eliminates the I/O write storm effectively.

Is it an issue of specific usage scenario or a general issue to be resolved?

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