Monitor Mac OS X HDD access

Question

I got an iMac 27" with a dying hard drive. Sometimes I got hight read/write access to the hard drive and I don't why.

Is there an program to monitor the access program specific? I want to know which program causes the high activities.

Answer 1

You can use the command-line application fs_usage to monitor disk use live. It requires elevated privileges.

Enter in Terminal:

sudo fs_usage

The only problem is, without filtering for applications, you probably won't be able to read the output fast enough. To filter for specific applications:

sudo fs_usage Finder

It wants the internal application name that is also used e.g. in ps, not the name of the application bundle.

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Another option is opensnoop: It only monitors file open activity and contains less noise than fs_usage but you need e.g. grep to filter the output.

It contains the numeric file descriptor returned from the file open call or -1 if it failed. This doesn't have to indicate a real problem though: Many programs seem to open files (e.g. configuration files) speculatively, and if they don't exist, fall back to defaults.

It also requires elevated (i.e. root) privileges:

sudo opensnoop

It's ideal for answering questions like this one: Run opensnoop | grep plist to monitor all .plist configuration file changes, and change some settings in System Preferences to find out where they're stored on disk.

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You can also inspect the processes in /Applications/Utilities/Activity Monitor.app. Select a process in the list, then View » Inspect Process » Open Files and Ports.

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You can also use fseventer, a GUI utility for monitoring file system changes.

(Thanks @Chealion!)