Alan, On 11/18/05 11:39 AM, "Alan Stange" <stange@xxxxxxxxxx> wrote: > Yes and no. The one cpu is clearly idle. The second cpu is 40% busy > and 60% idle (aka iowait in the above numbers). The "aka iowait" is the problem here - iowait is not idle (otherwise it would be in the "idle" column). Iowait is time spent waiting on blocking io calls. As another poster pointed out, you have a two CPU system, and during your scan, as predicted, one CPU went 100% busy on the seq scan. During iowait periods, the CPU can be context switched to other users, but as I pointed out earlier, that's not useful for getting response on decision support queries. Thanks for your data, it exemplifies many of the points brought up: - Lots of disks and expensive I/O hardware does not help improve performance on large table queries because I/O bandwidth does not scale beyond 110-120MB/s on the fastest CPUs - OLTP performance optimizations are different than decision support Regards, - Luke ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
