Move Time Machine to a Larger Disk – Mac Kung Fu, 2nd Edition

Tip 350Move Time Machine to a Larger Disk

If you use Time Machine, you might find the backup disk beginning to get full. You’ll know this because OS X will start to warn you that it’s deleting old backups to make space. The solution is to buy a bigger disk. Migrating your Time Machine backups to the new disk is easy. Here’s how. (These tips assume the disk is new and blank.)

  1. Attach the new backup disk directly to your computer’s port, rather than via a hub, to make the whole process of swapping backup disks much faster. Try to have a free USB/FireWire port on your computer ready for attaching to the old backup disk (although you shouldn’t do so at this stage).

  2. You’ll need to partition and format the new disk in a Mac-compatible way. Many commercial hard disks are preformatted for Windows, which your Mac can work with in normal circumstances, but Windows formatting isn’t compatible with Time Machine. Start Disk Utility. This can be found in the Utilities folder of the Applications list in Finder.

  3. In the Disk Utility window, select the new disk on the left side of the window (select the main entry for the disk and not the indented entry beneath that shows the partition). Ensure you select the new disk and not the old one, or you could accidentally wipe your old Time Machine data!

  4. Click the Partition tab within Disk Utility. Then, in the drop-down list beneath Partition Layout, select 1 Partition.

  5. Give the disk a name in the relevant field (something like New Time Machine would be great), and then make sure the Format drop-down reads Mac OS Extended (Journaled).

  6. Click the Options button. In the dialog box that appears, click the GUID Partition Table entry, and click OK. Finally, click the Apply button to partition the disk ready for use. This process might take a minute or two—watch the progress display at the bottom of the Disk Utility window.

  7. Once it’s finished, close Disk Utility and open Finder. Locate the new disk in the list in the side pane. Select it and hit Command+I.

  8. In the dialog box that appears, look at the very bottom. Expand Shared & Permissions, and ensure there’s not a check next to Ignore Ownerships on This Volume. If the box is checked, click the padlock icon to unlock the dialog, enter your password when prompted, and then click to remove the check. Close the info window when you’re done.

  9. Attach the old Time Machine disk, ideally in its own USB/FireWire port on your computer, rather than via a USB/FireWire hub. This will make the cloning process much faster. Then open System Preferences (Apple menuSystem Preferences), and click the Time Machine entry. Temporarily turn off Time Machine by clicking the switch.

  10. Open a Finder window and locate your old Time Machine disk under the Devices heading in the side pane. Browse the contents of the disk, and click and drag the Backups.backupd folder to the new Time Machine disk. This will copy across the backup files and will probably take some time to complete. Remember that while this is happening you aren’t protected by Time Machine backups, so it might be wise to avoid working on the computer for this period.

  11. Once the copy has finished, eject and remove the old Time Machine disk. Again, activate System Preferences, and click the Time Machine icon. Click the Select Disk button, and then select your new Time Machine disk. Then click the Use Disk button.

  12. Reactivate Time Machine by clicking the slider control.

This is all that’s required. Check that your new Time Machine disk works by entering Time Machine in the usual way and browsing back through your file history. Once you’re 100 percent sure everything is OK, it’s a wise idea to blank the old backup disk by repartitioning and reformatting it as described in the previous steps. If you don’t, each time you attach it to your computer OS X will attempt to make a backup to it, which could prove confusing.

If you find there’s an issue with the new Time Machine disk, simply turn off Time Machine, eject the new disk, and reattach the old disk before repeating all the previous steps to format the old disk for use with Time Machine.