Not all external disk drives are created equal. Some sleep, some don’t, but when they sleep it’s always at the wrong time so when I hit Command-O to open a file, the dialog box just sits there on my Mac’s screen while the external disks– backups, clones, Time Machine– spin up to speed from their slumber.
No, unchecking System Preferences > Energy Saver > Put Hard Disk To Sleep doesn’t work on external hard disk drives. They have a mind of their own, and every brand and model seems to have a different setting.
Here’s how to fix it for free.
If the external disk drives connected to your Mac sleep when they’re not supposed to and make you wait and grow whiskers while they spin up to speed, then install Keep Drive Spinning. It’s free.
This clever utility does the deed and periodically writes a little snippet of text to each connected disk drive (you choose which ones) so it can’t sleep. Keep Drive Spinning creates an OS X launch agent (a background technology built in to every new Mac) that does the deed, even after you shut down and restart your Mac.
The interface is drop dead simple. Double click Keep Drive Spinning and select Keep A Drive Awake. Select the disk you want to keep awake, set the time (the default of 60-seconds is perfect for most disk drives) and you’re done.
Repeat for additional disk drives. In fact, that’s the only oddity with Keep Drive Spinning. You have to repeat the process for each disk drive you want to keep spinning.
Regardless, it works. Every 60 seconds a file gets written to the external disk drives so they stay awake and don’t have a chance to sleep, ipso facto, ergo, no sleep disk drives and no spinning beach balls while you wait for the drive to wake up.