SAR

The SAR suite of utilities originated in Solaris. It became popular and now runs on most flavors of UNIX, including AIX, HP-UX, and Linux.

(System Activity Reporter)

The reason for sar creation was that gathering system activity data from vmstat and iostat is pretty time-consuming. If you try to automate the gathering of system activity data, and creation of periodic repots you naturally come to creation of a tool like sar.

System Activity Recorder can monitor half-dozen metrics related to overall system performance, for example:

cpu utilization (it's pretty effective tool for spotting CPU bottlenecks)

hard disk utilization

terminal IO

number of files open

      processes running