I have another client site that shoots up to 3,000 QPS, but I don't have the statistics of page access for it. This one has 4 Xeons 3.2GHZ each and 4GB. Write a simple script to run vmstat every 15 seconds or so, log the output to a file. Keep it running until the "hang" happens, and then see what it tells you about the system. Are you out of CPU? Do you have too many blocked processes or runable processes? Do you have a lot of wait on i/o? Are you swapping to the point of thrashing. Only after you do this analysis you should decide whether to upgrade the RAM or just tune things. Regarding decreasing the number of Apache processes, yes, that means you can only serve so many users, but you prevent the chaos caused by swapping. Think of it as a popular restaurant. If they let in more people than they have tables/seats, would the customer be happy? Would the staff cope with it?