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.
iostat are both part of the
sysstat package, we recommend that you review the Evaluating current disk performance with iostat recipe before continuing.