sar is a great general performance monitoring tool. sar can output data for almost everything Linux does. The sar command is delivered in the sysstat rpm.

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The top command is one of the most familiar performance tools. Most system administrators run top to see how their Linux and UNIX systems are performing. The top utility provides a great way to monitor the performance of processes and Linux as a whole. top can be run as a normal user as well as root.

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The iostat command is another tool for looking at disk throughput. Just like sar, iostat can be given the interval and count arguments. The output for the first interval contains metrics for the entire time Linux has been running. This is probably the most unique feature of iostat compared to other performance commands. The following output, from a system that is mostly idle, is a good example. You can see that the hda device has read about 9158MB (18755572*512/1024/1024) since boot up. The Blk columns are 512-byte blocks.

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Just like looking at the temperature gauge in a car, you need to keep an eye on the performance metrics of your Linux systems. The tools are:

• top
• sar
• vmstat
• iostat
• free

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