This is the second part of the question. The first part is what are you trying to do with the application server? The demands of an e-commerce site are drastically different from the demands of a publishing site that present information but doesn't receive any. And the demands of high-volume sites are totally different from those of low-volume sites.
Here are some general concerns with regard to availability and performance:1. Bandwidth and hardware up-time. Basics, not involved with application servers, but probably the most critical performance issues.
2. Security. In most cases, security degrades performance. Not just user log-in, but encryption, SSH, etc. all involve duplicate processing.
3. Memory. At least on Unix-based systems, seems to be more potent a performance indicator than raw processor power (and it's cheaper).
4. Synchronization (databases and application server instances). Distributed systems are generally more reliable, but there -is- a cost to network access.
Editor's note: To read about other important considerations for choosing an application server, visit http://searchmiddleware.stage.techtarget.com/ateQuestionNResponse/0,289625,sid26_cid396942_tax287611,00.html.
This was first published in July 2001