According to Heisenberg’s Principle, one cannot measure something without also affecting it in some way. When you measure the performance of a system, be aware of the effect that your measurement tools may have. Fortunately, most of the data collection utilities have a negligible impact on the system. A sar, vmstat, or iostat collecting data at 5-second intervals is not going to make a noticeable difference. Collecting a system call trace of an active process is an example of the kind of high-speed data collection that should be used with care.
Using Accounting to Monitor the Workload
If you have access to a group of end users over a long period of time, then enable the Unix system accounting logs. The logs can be useful ...