It's interesting that people focus on shared_buffers. From my
experience the most dominating parameter for performance is
wal_sync_method. It sometimes makes ~20% performance difference. On
the otherhand, shared_buffers does very little for
performance. Moreover too many shared_buffers cause performance
degration! I guess this is due to the poor design of bufmgr. Until it
is fixed, just increasing the number of shared_buffers a bit, say
1024, is enough IMHO.
--
Tatsuo Ishii