Disable Disk Sleep

How to disable disk sleep while still retaining functionality

If "Put hard disks to sleep when possible" is disabled in the Energy Saver Preference Pane, Mac OS automatically assumes that all devices are "awake". As a result, StorageStatus will also list devices as "awake". Further, StorageStatus will be unable to retrieve certain disk information (most notably time since disk activity) and there is currently no way to obtain this information while disk sleep is disabled. However, the same end result can be achieved while leaving the setting enabled within System Preferences.

By setting the idle timer to a large value (for example a week, or 10080 minutes), the disks will remain awake and Mac OS will also provide the necessary information to StorageStatus. This can be accomplished by executing the command below:

sudo pmset -a disksleep 10080

Higher values can be used if necessary, though a week is likely sufficient for the desired result.
For more information regarding using pmset to alter the idle threshold, please visit this page.