On Fri, Jan 27, 2006 at 08:23:55PM -0500, Mike Biamonte wrote: > This query took 18 hours on PG 8.1 on a Dual Xeon, RHEL3, (2.4 > Kernel) with RAID-10 (15K drives) and 12 GB Ram. I was expecting it > to take about 4 hours - based on some experience with a similar > dataset on a different machine (RH9, PG7.3 Dual Xeon, 4GB RAM, > Raid-5 10K drives) > > It's difficult to just "try" various ideas because each attempt > takes a full day to test. Real experience is needed here! It seems like you are changing multiple variables at the same time. I think you need to first compare the query plans with EXPLAIN SELECT to see if they are significantly different. Your upgrade from 7.3 to 8.1 may have resulted in a less optimal plan. Second, you should monitor your IO performance during the query execution and test it independent of postgres. Then compare the stats between the two systems. As a side note, if you have many disks and you are concerned about bottlenecks on read operations, RAID 5 may perform better than RAID 10. -Mike
