Moving Time Machine

Although the documentation says you can copy Time Machine backups in the Finder, it's very slow and sometimes doesn't work at all.

This technique will only work if the volume you're copying to is the same size, or larger than, the one you're copying from.

First, open the Time Machine preference pane and click the Options button. You may have to unlock the settings first by clicking the padlock icon in the lower left corner of the window. Authenticate as an administrator.

Delete the volume you're going to copy from the list of backup destinations. Then turn Time Machine OFF.

Launch Disk Utility, open the built-in help, and search for the term "Duplicate." Follow the instructions. All existing data on the destination volume will be erased. That shouldn't be a problem, because you don't want to mix backup and non-backup data on the same drive anyway.

In the Time Machine preference pane, turn it back ON and select the new volume as a backup destination. You can also continue to use the old volume, if you wish. The two will be alternated when both are available.

CAUTION: If the volume you're copying is corrupt, as shown by Repair Disk or Verify Disk in Disk Utility, then that corruption will be copied to the new drive. Don't copy data from a corrupt volume on a malfunctioning drive. Put the drive aside and don't use it until you're sure you'll no longer need the data. Then securely erase it and take it to a recycling center. Do the same if the Restore operation fails with "disk errors."

If the volume was encrypted by Time Machine, you have to unlock it first. Click the Unlock button in the toolbar.

No. In the Disk Utility window. The button shows only when a locked, encrypted volume is selected. If you don't know whether the volume is encrypted, the TM preference pane will show you.