One Mac, two Time Machine backups

Reader Carlo is interested in redundant Time Machine backups. He writes:

I’d like to have two Time Machine backup drives for my MacBook, one I use at home, and a smaller one for travel. Can this be done easily? Can the two volumes have the same name?

It can be done easily and the two volumes can have the same name.

To do it, simply attach the drive you’ll use at home, open the Time Machine system preference, click the Select Disk button, and choose the attached drive as the backup destination. Initiate a backup and wait until it’s done.

Now attach the other drive, open the Time Machine system preference yet again, click Select Disk, and choose the new drive as the backup destination. Again, wait for the backup to complete. You now have two identical backups.

Naturally your two Time Machine backups will be out of sync once you do something on your Mac and the next backup completes—the drive you last attached will have the most up-to-date backup. However, when you plug in the other drive and choose it as the backup destination, it will update the backup from the point where it (that particular drive) last left off, not from the point where Time Machines believes it last backed up the Mac.

There’s no great advantage to providing your two drives with the same name. Time Machine uses information other than a device’s name to identify it. So, for example, you could name both of your drives “Backup Drive” and you’d still have to click Time Machine’s Select Disk button and choose the drive you've attached each time you switch drives.

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