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