"Monitoring itself can be broken down into two broad parts. The
first is actually determining which metrics are needed and then
collecting that data from the hosts. Some of the most commonly
tracked metrics are CPU usage, memory consumption, network
bandwidth, and disk I/O stats. These provide different indications
of how well a system is performing, and may indicate where there
are potential problems or performance bottlenecks. Once the data
have actually been acquired, the second task is presenting the
information in a meaningful way for analysis."