The following has been copied form an article that can be found at ‘How To Move OS X Time Machine Backups To A New Disk‘
- Turn off Time Machine with the big switch in the Time Machine System Preferences panel.
- Eject the old Time Machine disk, unplug it, and re-insert it to force it to re-mount as a regular drive.
- Use Disk Utility to wipe the new drive completely. Give it a single partition ( Apple recommends using GUID partition maps to avoid Time Machine trouble!) and a new empty filesystem. Time Machine requires the filesystem to be of the type, “Mac OS Extended (Journaled)”.
- Give the new drive a unique name so you can keep them straight when you’re copying.
- Plug both drives into your Mac. You should see both in the Disk Utility sidebar.
- Select the “Restore” tab in Disk Utility. This built-in OS X application can create a perfect block copy of your Time Machine drive, no third-party tools required.
- Drag your old drive from the sidebar to the “Source” box.
- Drag your new drive from the sidebar to the “Destination” box.
- Click “Restore” and observe the warning – this will copy all data from your old Time Machine volume to the new drive, destroying its contents!
- Wait a long while a
- Once it’s done, unplug the old drive and turn Time Machine back on. Make sure that it located the data on the new drive by clicking the Enter Time Machine item in the dock and looking at your old data.
- Consider telling Spotlight not to index this new drive or at least the “Backups.backupdb” folder.
- Once you’re satisfied that the new drive is working, you may want to use the old drive for something else. If so, turn Time Machine off again, plug in only the old drive, and erase it with Disk Utility. Don’t switch back and forth between the two Time Machine drives or you will become hopelessly confused!