Mark,
> No manual vacuum commands before. The decline in performance has been
> pretty consistent in all my previous tests and people have told me on
> many occasions that the decline in performance was probably because I
> was never using vacuum...
Hmmm ... what autovacuum params are you using? From the look of the graphs,
VACUUM is running every 6 minutes or so, and having a huge impact on
performance when it does run. Give me a bit of time to crunch the database
log, and we'll see which table vacuums were taking the most time.
Can you re-run this test with a fairly generous vacuum_delay setting? Given
that the performance drops seem to correspond to wait times, I think this
could mean a big difference.
--
Josh Berkus
Aglio Database Solutions
San Francisco