I've been studying the slow forum response time issue for some time now and it is due to the log file statistics collection program. The program runs automatically at the top of every hour and usually takes about 5 minutes to complete. But I have seen cases where it can take as long as 30 minutes.
If forum traffic is particulary heavy, memory will begin swapping to disk until enough is available for the statistics collection program, which runs as a high priority task.
Another bottleneck is disk contention. At the end of the day, the log file is around 300 MB in size. The statistics collection program only processes new transactions since the last time it was run, but a significant amount of disk i/o takes place in order to get to that first transaction record.
A bigger issue with disk contention is that we only have one physical hard drive on the server. If we had two physical drives, the forum database could be put on its own hard drive.
The good news is that our CPU utilization is low
Red Hat takes full advantage of the Pentium 4's hyperthreading capabilities!