Re: New to PostgreSQL, performance considerations

Alexander Staubo <alex@purefiction.net> writes:
> No, fsync=on. The tps values are similarly unstable with fsync=off,
> though -- I'm seeing bursts of high tps values followed by low-tps
> valleys, a kind of staccato flow indicative of a write caching being
> filled up and flushed.

It's notoriously hard to get repeatable numbers out of pgbench :-(

A couple of tips:
    * don't put any faith in short runs.  I usually use -t 1000
      plus -c whatever.
    * make sure you loaded the database (pgbench -i) with a scale
      factor (-s) at least equal to the maximum -c you want to test.
      Otherwise you're mostly measuring update contention.
    * pay attention to when checkpoints occur.  You probably need
      to increase checkpoint_segments if you want pgbench not to be
      checkpoint-bound.

            regards, tom lane