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Re: Tuning

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Josh Berkus <josh(at)agliodbs(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org, "John Parnefjord" <John(dot)Parnefjord(at)kib(dot)ki(dot)se>
Subject: Re: Tuning
Date: 2007-01-28 23:38:18
Message-ID: 26422.1170027498@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
Josh Berkus <josh(at)agliodbs(dot)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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  • Re: Tuning at 2007-01-28 23:24:24 from Josh Berkus

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