Re: Tuning

Josh Berkus <josh@agliodbs.com> writes:
>> -checkpoint_segments - this is crucial as one of the server is
>> transaction heavy

> Well, it only helps you to raise this if you have a dedicated disk resource
> for the xlog.   Otherwise having more segments doesn't help you much.

Au contraire, large checkpoint_segments is important for write-intensive
workloads no matter what your disk layout is.  If it's too small then
you'll checkpoint too often, and the resulting increase in page-image
writes will hurt.  A lot.

My advice is to set checkpoint_warning to the same value as
checkpoint_timeout (typically 5 minutes or so) and then keep an eye on
the postmaster log for awhile.  If you see more than a few "checkpoints
are occuring too frequently" messages, you want to raise
checkpoint_segments.

            regards, tom lane