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@2ndQuadrant.com   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.com