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Re: Postgres 9.1.4 - high stats collector IO usage

From: Magnus Hagander <magnus(at)hagander(dot)net>
To: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
Cc: David Barton <dave(at)oneit(dot)com(dot)au>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Postgres 9.1.4 - high stats collector IO usage
Date: 2012-08-06 14:18:49
Message-ID: CABUevEwA7gqn0OCahWx41T74-AEc8UG2EjLWkSxwQxmAqCn=Og@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Mon, Aug 6, 2012 at 4:16 PM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
> 2012/8/6 Magnus Hagander <magnus(at)hagander(dot)net>:
>> That's not a good way of doing it, since you loose persistent storage.
>>
>> Instead, you should set the stats_temp_dir paramter to a filesystem
>> somewhere else that is tmpfs. Then PostgreSQL will automatically move
>> the file to and from the main data directory on startup and shutdown,
>> so you get both the performance of tmpfs and the persistent
>> statistics.
>
> we had to do it because our read/write of  stat file created really
> high IO - and it was problem on Amazon :( - probably we had not this
> issue elsewhere

Uh. You realize that if you set stats_temp_dir, it only ever writes to
the persistent storage once, when you do "pg_ctl stop" (or
equivalent). Are you saying the shutdown took too long?

I've had to change that param many times on Amazon, but I've never had
a problem with the shutdown writes. (And I've seen it often enough on
dedicated hardware as well..)

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

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