How can I tell if writing to the WAL is a bottleneck? In other words, how can I tell if upgrading the disk the WAL is on will improve performance? (I do have the WAL on its own disk.)
I ask because my understanding is that if the WAL disk is fast enough, performance will be virtually identical to running with fsync off. But, I don't know how to tell how fast is "enough" for my service...
[I mailed this twice to pgsql-general. First time it bounced because their list manager screwed up my subscription info after it being fine for many months. Second time it just disappeared into the ether -- real professional, guys. So, I'm hoping someone here can help out.]
