Beef Up Your Time Machine Backup With Multiple Disks

Apple’s Time Machine has proven to be more than adequate for providing a solid backup and recovery option single Macs to small networks. Easy to setup and understand, Time Machine runs silently in the background, protecting as much data history as the destination drive has room for.
A new feature in Mountain Lion (OS X 10.8) now allows for increased data protection with the ability to create multiple backup copies to more than one disk.  This new feature is as powerful as it is easy to set up, but it’s fairly hidden away from view. Let’s uncover it.

System Preferences

Time Machine is a Preference Pane found in System Preferences (Apple Menu > System Preferences…). Click on it’s icon and then on the Select Disk… button 1.

The Select Disk window will display the disk you are currently backing up to on top (Backup Disks 2) and other backup-ready disks below (Available Disks 3). HINT: if networked drives are not displaying in the list, you may have to mount them in the Finder first.

Use Both!

So adding additional disks to your Time Machine backup is as simple as making the selection from the list and clicking the Use Disk button, and then the Use Both button. Your Mac will take care of the rest.

Your data will be copied to one disk on the first backup and the additional disk on the second backup, rotating back and forth to keep both disks as current as possible.

The Time Machine Backup Scheme

It’s not rare that the hard drive in the Mac is bigger than the drive that it is backing up to. Time Machine will do its best to use the available space by deleting the oldest data in a rotating fashion, replacing it with a fresh backup.

With Mountain Lion, it is now possible to enhance the security of your data by using multiple disks to create more than one backup of your hard drive.

Better still, Use Both makes a rotating, off-site-storage option possible. Since Time Machine  will scan for the disks you’ve specified, if only one is available at backup time, that disk will be used until the additional disk(s) become available. Data security is increase by 1) duplication of backup data and, 2) extending the history of backup.

Study the Time Machine Keeps: section of the Preference Pane window 5 (Figure 1) for a better understanding of the Time Machine backup scheme.