Time Machine Backup Trouble

If your Time Machine backup fails, try these fixes:

  • Restart your computer and try the backup again. i.e. use the menu bar TM icon and select “Backup Now” after your restart.
  • Make sure your computer’s name doesn’t include the characters ? or /. You’ll find the name in System Preferences > Sharing
  • Make sure your backup drive’s name doesn’t have ? or /.

There are lots of hints on Apple’s Time Machine Troubleshooting page.

If you believe that the data on your TM drive may need to be repaired:

  • Turn off TM from within its Preferences.
  • Use Disk Utility (Applications > Utilities) to “Repair Disk”.

If your Mac is freezing up when TM runs, and you’ve found yourself needing to force a restart or power down:

  • With your Mac’s power off, disconnect your TM drive.
  • Power up your Mac.
  • Turn off TM from within its Preferences.
  • Attach your TM hard drive and power it up.
  • Use Disk Utility (Applications > Utilities) to “Repair Disk”.

Formatting your hard drive:

Note: Connect your HD directly to your computer for formatting. Once connected and powered up, run Disk Utility.

Your HD must be properly formatted to work with TM. The HD must use a Partition Map Scheme of either GUID Partition Table (for Intel Macs) or Apple Partition Map (for PPC Macs).

Partition Map Scheme
Partition Map Scheme

It must also use a Format of Mac OS Extended (Journaled).



Below you’ll find miscellaneous notes about Time Machine. Many were gleaned from MacWorld forums.

Moving Time Machine to a new hard drive:

This may may be required if you get a larger drive for TM or if you need to reformat your existing TM drive. Dragging your old TM backup folder to a new drive does NOT work.

  • SuperDuper (v2.5 or greater ~ $28) can copy a TM volume — Update TM hard drive — Use SuperDuper to copy back.
  • Disk Utility (in your Application folder) can be used to create a .dmg of the TM volume — Update TM hard drive — Restore (with Erase Disk Option set).

Hard drive partitioning & formatting:

  • If your hard drive’s Partition Map Scheme is MBR (Master Block Record) then the maximum partition size is 512GB.
  • Don’t use MBR as your partition scheme unless you need it for compatibility with DOS/Windows.
  • Always use either APM (Apple Partition Map) or GUID (Globally Unique Identifier) as your drive’s Partition Map Scheme.
  • Intel based Macs should use GUID partition map.
  • PPC based Macs should use APM.
  • Each partition has its own format.
  • Format your TM partition as “Mac OS Extended (Journaled)”. This format is also known as HFS+ (Hierarchical File System Plus)

What Time Machine shouldn’t backup:

  • Disk images (encrypted or not) within which you make minor changes. TM will backup the entire image with every change made to these images.
  • Parallels and Fusion images.


  • Get rid of unwanted TM files: Within TM, the Finder-window button-bar has a “gear” drop down menu. Select “Delete All Backups of …” If you don’t see the “gear” you may need to add it using the menu: View — Customize Toolbar…
  • Want to change how often Time Machine backs-up your files? Use TimeMachineEditor (free).
  • You may want to turn off TM, if you’re doing lots of file intensive work. Turn it back on when you’re done.
  • If you reorganize your hard drive, and move around a bunch of files, it can take some time for the next TM backup to complete.
  • If TM is interrupted, you may corrupt your backup storage. Interrupted includes: force quit, unplug the hard drive, unplug the computer, or force a power down.
  • You can use TM to backup to a hard drive connected to an Airport Extreme – over ethernet or Wi-Fi (I haven’t tried this). Be sure that your Wi-Fi uses a password or it may not work properly with TM.
  • Using NAS (network attached storage) drive may work with TM. Not sure it’s a good idea… but maybe. NetGear