If you had to do capacity planning and hardware sizing "BEFORE" you had a chance to actually code and test the application (typically while you are defining solution architecture), how would you do it?
I know this can not be known accurately beforehand but the point is to present the approach at an early stage (including questions you need to ask, assumptions you need to make).
All you know, it will be an enterprise java application with App server, Web Server, Database. Business has given some number of concurrent "USERES" say 1000. Also assume that you will get a chance to fine tune your numbers after load testing the application but you can't be far off from the original estimates.