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Single vs. Multiple (Core) Processors
When purchasing production machines the general rule is "greater horsepower and more horsepower". This doesn't hold true with the !IdP. Java applications scale poorly across multiple processors (or processor cores). The most common JVM, Sun's, uses one processor core to run all of its Java code (it may use other cores for other tasks as discussed below). So, processor speed is the place to sink your money, not the number of coresUnlike most web applications the IdP is CPU bound, because of the large number of cryptographic operations performed. Most multi-core systems sacrifice some CPU speed, because of thermal issues, in order to get more cores on the CPU. Since Java 1.5 most JVMs do now scale across cores but it is our recommendation that faster cores, over more cores, is still the better option. This results in lower response times (because the crypto operations are performed more quickly) but slightly less overall throughput.
Software
Generally the IdP is run within Tomcat with an Apache HTTP server front-end. Apache 2 and Java 1.5 are recommended. Be sure to tune both Apache and the JVM used by Tomcat appropriately.
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