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Re: wal_level=archive gives better performance than minimal - why?

From: Greg Smith <greg(at)2ndQuadrant(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: wal_level=archive gives better performance than minimal - why?
Date: 2012-01-16 22:35:53
Message-ID: 4F14A649.5060501@2ndQuadrant.com (view raw or flat)
Thread:
Lists: pgsql-performance
On 01/12/2012 06:17 PM, Tomas Vondra wrote:
> I've run a series fo pgbench benchmarks with the aim to see the effect
> of moving the WAL logs to a separate drive, and one thing that really
> surprised me is that the archive log level seems to give much better
> performance than minimal log level.

How repeatable is this?  If you always run minimal first and then 
archive, that might be the actual cause of the difference.  In this 
situation I would normally run this 12 times, with this sort of pattern:

minimal
minimal
minimal
archive
archive
archive
minimal
minimal
minimal
archive
archive
archive

To make sure the difference wasn't some variation on "gets slower after 
each run".  pgbench suffers a lot from problems in that class.

-- 
Greg Smith   2ndQuadrant US    greg(at)2ndQuadrant(dot)com   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.com


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Subject: Re: wal_level=archive gives better performance than minimal - why?
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