While there are many tools to view or analyze the current server performance and behavior, how do we examine historical activity? Most Linux systems rotate logfiles in /var/log for varying periods of time. Unfortunately, these are programs and system logs, not performance measurements.
When we installed the sysstat package in a previous recipe, we gained the use of the sar utility. Some argue that sar is the Swiss Army knife of metric collection. A simple invocation can display past data regarding memory, CPUs, IRQs, disk devices, networks, or even TTYs.
When administering a highly-available server, there are few things as helpful as performance trends. Let's examine them.
