Tip: Monitor disk usage in Mac OS X 10.2.x

Mac OS X ships with a tool that can be used in the Terminal to monitor every disk access on the system. If something is polling your system's hard drive every (however many) seconds, the tool can be used to determine exactly what it is.

This tip can be useful for diagnosing a number of problems, and we are currently using it to investigate the mysterious clicking issue that erupted after Mac OS X 10.2.5's release.

The UNIX command is 'fs_usage'. 'man fs_usage' in a terminal will give detailed information. It needs to be run as root (or via 'sudo'). It produces a spool of output that you can either see immediately or redirect into a file that can be viewed later:

• go to Terminal
• execute: sudo fs_usage -w -w

Or:

• sudo fs_usage -w -w > output.txt (click on the window and hit control-c when you want to stop fs_usage, then 'open output.txt')

fs_usage can also be used to monitor specific applications, as such:

• sudo fs_usage -w -w Safari
• sudo fs_usage -w -w Finder

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