Mac OS X 10.5: Time Machine stops backing up to external disk

After about 10 GB or more of data is backed up to an external disk, Time Machine may stop backing up. This may happen the first time Time Machine backs up your files.

Some hard disks ship with a Master Boot Record (MBR) partition type. For these disks, you will need to change the partition type by erasing the disk, so that it is supported by Time Machine:

Important: Erasing a disk deletes all files on it. Make sure that you have or make a separate backup copy of important files, in another location, first.

  1. Open Disk Utility.
  2. Select the backup disk's icon on the left side of the window, which usually appears with a numerical capacity and is offset slightly to the left of any volume icons. If you see a tab named "Partition" appear, proceed to step 3.
  3. Click the Partition tab. (If you only see tabs named First Aid, Erase, RAID, Restore, then you have selected a volume on the disk instead of the disk itself--repeat step 2.)
  4. From the Volume Scheme pop-up menu, choose the desired number of partitions (or 1).
  5. Click the "Options..." button.
  6. Select a new partition scheme:
    • Use Apple Partition Map partition scheme if the disk will be used with Time Machine and a PowerPC-based Mac.
    • Use GUID partition scheme if the disk will be used with Time Machine and a Intel-based Mac.
  7. Click OK.
  8. Click Apply. This will erase the disk.

Once the external hard disk is repartitioned, select it again in Time Machine preferences and use it for your backups.

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