Time Machine pauses when your Mac sleeps
Time Machine is supposed to back up your Mac automatically. And it does, as long as your Mac is awake. The moment macOS goes to sleep, Time Machine pauses. It'll resume when you wake up, but if you're running a large initial backup or backing up after weeks of changes, that backup can take hours. If your Mac keeps sleeping in the middle of it, a backup that should take 3 hours ends up taking all day because it keeps stopping and starting.
This is especially painful for first-time backups. You plug in a new external drive, Time Machine starts copying hundreds of gigabytes, and you walk away. Your Mac sleeps after 10 minutes. The backup pauses. You come back, wake the Mac, the backup resumes. You walk away again. It sleeps again. The cycle repeats until you're frustrated enough to sit there and babysit it.
The external disk condition
Shake It On has a condition called "Only Shake If external disk connected." This is basically built for the Time Machine use case. Here's how it works: when you plug in your backup drive, Shake It On detects the external disk and starts keeping your Mac awake. When you unplug the drive (because the backup is done or you're taking your laptop somewhere), shaking stops automatically and your Mac goes back to sleeping normally.
You don't have to toggle anything. You don't have to remember to turn Shake It On on before a backup or off after. The presence of the external drive is the signal. Plug in, stay awake. Unplug, sleep normally.
This works with any external drive, not just Time Machine volumes. If you're copying a large folder to an external SSD or cloning a drive with Carbon Copy Cloner, the same condition applies.
Recommended setup for backups
Here's how to configure Shake It On for Time Machine:
- Enable "Only Shake If external disk connected." This is the core condition. Shaking only happens when a drive is plugged in.
- Enable "Paused When on battery." Large backups use a lot of disk I/O, which drains battery fast. If you're backing up, you should be plugged in. This condition makes sure your MacBook doesn't drain itself keeping awake for a backup on battery power.
- Enable "Allow display to sleep." The display doesn't need to be on for a backup to run. Let the screen turn off while the system stays awake and Time Machine keeps copying.
- Set "Launch at login." You want this running automatically so you never have to think about it. Plug in the drive, the backup runs, the Mac stays awake. That's it.