From: Greg Smith <gsmith@gregsmith.com>
To: Henrik <henke@mac.se>
Cc: pgsql-performance@postgresql.org
Subject: Re: Hardware suggestions for high performance 8.3
Date: Wed, 25 Jun 2008 11:45:43 -0400 (EDT)
Message-ID: <Pine.GSO.4.64.0806251127470.29204@westnet.com> (raw)
In-Reply-To: <A928E958-6E18-4636-B578-31A131822B64@mac.se>
References: <2B6702BC-3513-407E-AAC2-7E04299CA237@mac.se>
<Pine.LNX.4.64.0806251210520.5056@aragorn.flymine.org>
<A928E958-6E18-4636-B578-31A131822B64@mac.se>
On Wed, 25 Jun 2008, Henrik wrote:
> Would you turn off fsync if you had a controller with BBU? =)
Turning off fsync has some potential to introduce problems even in that
environment, so better not to do that. The issue is that you might have,
say, 1GB of OS-level cache but 256MB of BBU cache, and if you turn fsync
off it won't force the OS cache out to the controller when it's supposed
to and that can cause corruption.
Also, if you've got a controller with BBU, the overhead of fsync for
regular writes is low enough that you don't really need to turn it off.
If writes are cached the fsync is almost free.
--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD
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To: pgsql-performance@postgresql.org
Cc: gsmith@gregsmith.com, henke@mac.se
Subject: Re: Hardware suggestions for high performance 8.3
In-Reply-To: <Pine.GSO.4.64.0806251127470.29204@westnet.com>
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