From: Tom Lane <tgl@sss.pgh.pa.us>
To: Josh Berkus <josh@agliodbs.com>
Cc: pgsql-performance@postgresql.org, "John Parnefjord" <John.Parnefjord@kib.ki.se>
Subject: Re: Tuning
Date: Sun, 28 Jan 2007 18:38:18 -0500
Message-ID: <26422.1170027498@sss.pgh.pa.us> (raw)
In-Reply-To: <200701281524.24317.josh@agliodbs.com>
References: <76C73999206F3145A2E3046A5C32A103F02A5A@kibmail.kib.local>
<200701281524.24317.josh@agliodbs.com>
Josh Berkus <josh@agliodbs.com> writes:
>> -checkpoint_segments - this is crucial as one of the server is
>> transaction heavy
> Well, it only helps you to raise this if you have a dedicated disk resource
> for the xlog. Otherwise having more segments doesn't help you much.
Au contraire, large checkpoint_segments is important for write-intensive
workloads no matter what your disk layout is. If it's too small then
you'll checkpoint too often, and the resulting increase in page-image
writes will hurt. A lot.
My advice is to set checkpoint_warning to the same value as
checkpoint_timeout (typically 5 minutes or so) and then keep an eye on
the postmaster log for awhile. If you see more than a few "checkpoints
are occuring too frequently" messages, you want to raise
checkpoint_segments.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, josh@agliodbs.com, John.Parnefjord@kib.ki.se
Subject: Re: Tuning
In-Reply-To: <26422.1170027498@sss.pgh.pa.us>
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