dstat – one hell of an awsome performance monitoring tool
Dstat is a versatile replacement for vmstat, iostat, netstat, nfsstat and ifstat. Dstat overcomes some of their limitations and adds some extra features, more counters and flexibility. Dstat is handy for monitoring systems during performance tuning tests, benchmarks or troubleshooting.
Dstat allows you to view all of your system resources instantly, you can eg. compare disk usage in combination with interrupts from your IDE controller, or compare the network bandwidth numbers directly with the disk throughput (in the same interval).
This has to be my most favourite bit of software right about now. You can download it from http://dag.wieers.com/home-made/dstat/ or get it via your distros package manager.
It really helps you find the bottle neck in a system without having 10 terminals open.