Re: Doc patch making firm recommendation for setting the value of commit_delay

On 11/15/12 12:19 AM, Albe Laurenz wrote:
> If there is an agreement that half the sync time as reported by
> pg_test_fsync is a good value, would it make sense to have initdb test
> sync time and preset commit_delay?

Peter has validated this against a good range of systems, but it would
be optimistic to say it's a universal idea.

My main concern with this would be the relatively common practice of
moving the pg_xlog directory after initdb time. Sometimes people don't
know about the option to have initdb move it. Sometimes the drive to
hold pg_xlog isn't available when the database is originally created
yet. And the camp I fall into (which admittedly is the group who can
take care of this on their own) will move pg_xlog manually and symlink
it on their own, because that's what we're used to.

I would rather see this just turn into one of the things a more general
tuning tool knew how to do, executing against a fully setup system.
Having a useful implementation of commit_delay and useful docs on it
seems like enough of a jump forward for one release. Moving fully into
auto-tuning before getting more field feedback on how that works out is
pretty aggressive.

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