On Fri, 07 Apr 2006 15:24:18 -0500 Scott Marlowe <smarlowe@xxxxxxxxxxxxxxxxx> wrote: > > See reply to Tom Lane :) > > I didn't see one go by yet... Could be sitting in the queue. If it's not arrived by now - EXPLAIN ANALYZE doesn't tell me anything :) > Let us know if changing the fsync setting helps. Hopefully that's all > the problem is. fsync's already off - yes a bit scary, but our I/O is only about 500KB/sec writing.. the whole db fits in RAM / kernel disk cache, and I'd rather have performance than security at this exact moment.. > Off on a tangent. If the aggregate memory bandwidth of the pSeries is > no greater than you Xeon you might not see a big improvement if you > were memory bound before. If you were CPU bound, you may or may not > see an improvement. I did look into the specs of the system, and the memory bw on the pSeries was /much/ greater than the Xeon - it's one of the things that really pushed me towards it in the end. I forget the figures, but it was 3 or 4 times greater. > Can you describe the disc subsystems in the two machines for us? What > kind of read / write load you have? It could be the older box was > running on IDE drives with fake fsync responses which would lie, be > fast, but not reliable in case of a power outage. Again, I'm confident that I/O's not the killer here.. the Xeon is a Dell 6850- hardware RAID1.. SCSI drives. > > Multi-Opteron was the other thing we considered but decided to give > > 'Big Iron' UNIX a whirl... > > It still might be a good choice, if it's a simple misconfiguration > issue. > > But man, those new multiple core opterons can make some impressive > machines for very little money. So I see - we could buy two quad-opterons for the cost of renting this pSeries for a month.... Cheers, Gavin.
