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

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@2ndQuadrant.com   Baltimore, MD
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