Back up your Mac to two drives and keep one somewhere else

Why it happens

One backup drive is good, but a fire, theft or flood can take it along with your Mac. Time Machine can use more than one drive and backs up to whichever is connected. Keep one at home and one at work or with family, and swap them now and then.

How to fix it

1. Connect the second drive to your Mac.

2. Open System Settings, click General, then Time Machine. Your current backup disk is listed there.

   General›Time Machine

3. Click the + button below the list, choose the new drive and click Set Up Disk. Turning on Encrypt Backup is wise for a drive you keep away from home; store that password somewhere safe.

4. If Time Machine needs to erase the drive, it warns you first. Everything already on it will be deleted, so copy off anything you want to keep.

5. From now on, Time Machine backs up to each drive in turn while it's connected. When you bring the away drive back, it catches up at its next backup.

If no backup disk is set up yet, you'll see the Add Backup Disk button instead of the + button. On macOS 27 it reads Add Backup Disk… with dots.

Still not fixed?

1. No + button? With no disk set up yet, click Add Backup Disk instead and pick your first drive.

   macOS 26 Tahoe General›Time Machine›Add Backup Disk

   macOS 27 Golden Gate General›Time Machine›Add Backup Disk…

2. If the new drive isn't offered, check it shows in Finder. Try another cable or port, and plug it straight into the Mac rather than a hub.

3. Bring the away drive back regularly, for example once a month, so its copy doesn't get too old.

4. If one drive keeps disconnecting, makes clicking sounds or gives errors with a new cable, it's probably failing and should be replaced. If every drive misbehaves on the same port, contact Apple Support or a repair shop about the Mac.