How do I choose what memory usage settings to use?

Question:

Making the right settings in the Memory Usage section of the control panel is more of an art than a science.

Answer:

Our recommendation is that for optimum performance the disk cache in Web Crossing (Memory Usage control panel) be set to about 1/3 to 1/2 of database size. If available RAM makes that impossible, it's wise to consider deleting some discussions then repacking the database to shrink the size.

Loosely, and realizing every system is very unique, figure a 10 msec delay for each disk page. So for example, 200 pages/minute is about 2 seconds of lost CPU time per 60 seconds, or 3.3% which is just fine.

Also, since there are a lot of disk reads during startup to init the disk cache, so the lost time is actually less than this. The thing to do is write down the loads and time, then check in 24 hours and see how it is doing.

The small object heap is a bit more of a problem, the best setting here is determined by watching the number of memory reclaims over time. Ideally the number would be small, perhaps a few thousand in a 24-hour period, but limitations on server RAM may require restricting the amount of memory Web Crossing can be allocated. The best approach is to make a modest change, then check again in 24 hours to see the result. Adjustments over a few days will allow you to reach a reasonable compromise between Web Crossing performance and other server requirements.

Please note! We DO NOT recommend that you increase your memory settings to the point where the majority of the memory being used by Web Crossing is VIRTUAL. Over use of virtual memory (which comes from your disk drive) is a severe performance killer. No disk is as fast as RAM.