How does performance scale when adding CPUs and servers ?
ANot surprisingly, the best cost/benefit ratio appears to come from upgrading a single-CPU iAS server to a pair of single-CPU servers. However, it is also cost-effective to increase the number of CPUs per server, certainly up to four, and perhaps up to eight. Acceptable performance benefits continue to accrue up until about 12 CPUs per server, but cost/benefit ratios are unlikely to be favourable for more than 12 CPUs. If you are using clustering, increasing from two servers to three gives significantly better results than increasing from three to four; little is achieved by having more than four servers in a group. This suggests that the largest single iAS cluster that should be contemplated is four servers with twelve CPUs each. This appears to be the case whether applications are using predominantly Web components or predominantly EJBs. If you are not using clustering, scaling beyond four servers can still be effectice.Bear in mind that clustering allows the use of distributed sessi
