How to profile resource usage and load?

[danep]

I am running a web server with a fairly low number of visitors every day (tens to hundreds of page requests), but on hardware that's almost a decade old. I am interested in profiling especially CPU and memory usage to see what the average load is from day to day, how high peak loads are, and how often loads hit 100%, so I can gauge bottlenecks and have an idea of what specs to choose for replacement hardware. Does anyone have suggestions for processes or software to accomplish this?

Thanks!