Mac Kung Fu, 2nd Edition

Tip 274

Sleep Hard Disks Sooner

Portable Macs include a feature in the Energy Saver pane of System Preferences that will put the hard disk to sleep when it isn’t being used (for example, if you’re simply browsing the Internet while out and about and not editing files). This can save battery life, especially if your Mac uses traditional mechanical hard disks rather than solid-state disks, but it kicks in only after ten minutes of inactivity—that is, ten minutes after the disk has not been written to or read from.

Going to Sleep Faster

You can reduce this time delay at the command line, causing the hard disk to go to sleep faster. You might find this helps save battery life, although there might be a very brief system freeze each time as the hard ...