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.
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