How To Move OS X Time Machine Backups To A New Disk

Well, that happened pretty quickly!  After upgrading the internal hard drive on my MacBook Pro to 320 GB, I moved the 120 GB disk Apple shipped with the machine to my Verbatim SmartDisk FireWire+USB enclosure to use as a Time Machine backup target.  Despite applying some tricks to reduce the amount of data backed up by Time Machine, I filled up the 120 GB drive pretty quickly indeed!  So I decided to swap the 160 GB drive from my Maxtor OneTouch 4 Mini USB drive into the (faster) Verbatim FireWire enclosure to give Time Machine some (temporary) breathing room.

It turns out that you can move Time Machine backups easily, with included OS X tools, and without breaking anything.  My old backups are still visible, and I have another 40 GB to work with.  Read on for the details!

The Windup

In order to effectively use Time Machine, you really need a backup target disk larger than the one you’re backing up.  But I didn’t have that.  I was able to prune out 28 GB of data in my home directory that didn’t need to be backed up, along with 22 GB of operating system data, by tuning Time Machine.  Although my lappie has over 300 GB of storage space, Time Machine only has to back up 66 GB of it – Windows Vista has 55 GB, 50 GB doesn’t need to be backed up, and the rest is empty.

The little 111 GB (usable) backup drive that I created when I stuffed the Fujitsu MH2120BH disk that came with my MacBook Pro into the vacated Verbatim enclosure that donated its Western Digital WD3200BEVT to my laptop was enough for a while.  But this wouldn’t be enough for long:  Time Machine currently takes up 103 GB to store a month and a half worth of my system backups.

Since I already had a 160 GB Maxtor OneTouch Mini 4 USB drive sitting around half full for Windows backups, I decided to swap the disk drive units between enclosures to get an extra 40 GB for Time Machine.  It turns out the Maxtor used a Seagate ST9160821AS drive, by the way.

Why not leave the drives in place and just use the Maxtor for Time Machine?  Three reasons:

1. FireWire is substantially faster than USB 2.0 (as I’ll show in a future post)
2. My MacBook has just one USB port that would work with the Maxtor, and I like to leave the Time Machine drive plugged in when I’m home, which would leave me with a hub (which I don’t have) or only a single USB port for everything else
3. I’m a nut and love to rip things apart and tinker with them

Most people will probably want to just go out and buy a bigger disk.

Moving Your Time Machine Data

Let’s say you have an old (full) Time Machine disk and a new (empty) one and you’d like to preserve your old backups.  Here’s how to move the Time Machine data without losing anything:

1. Turn off Time Machine with the big switch in the Time Machine System Preferences panel.
2. Eject the old Time Machine disk, unplug it, and re-insert it to force it to re-mount as a regular drive.
3. Use Disk Utility to wipe the new drive completely.  Give it a single partition (I chose MBR since it’s a removable drive, but it shouldn’t matter 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)”.



4. Give the new drive a unique name so you can keep them straight when you’re copying.  I recommend calling it “New Time Machine Drive” or something equally unambiguous.  I called mine “Verbatim 160” (even though it was still in the Maxtor case), while my old drive was called “Verbatim”.
5. Plug both drives into your Mac.  You should see both in the Disk Utility sidebar. See my example at right, showing both “Verbatim” and “Verbatim 160”.
6. 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.
7. Drag your old drive from the sidebar to the “Source” box.
8. Drag your new drive from the sidebar to the “Destination” box.
9. Click “Restore” and observe the warning – this will copy all data from your old Time Machine volume to the new drive, destroying its contents!
10. Wait a long while (mine took 4 hours) as the copy and verification progresses.



11. 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.
12. Consider telling Spotlight not to index this new drive or at least the “Backups.backupdb” folder.
13. 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!

So there you have it!  Move your Time Machine backup data with ease, using only OS X’s Disk Utility! This tool is amazingly good, making me wonder why anyone would need a third-party product.

Update: See Rolfje’s blog for streamlined Time Machine migration steps.

Problems

If the Restore process reports “Could not restore – operation not permitted“, you have to eject the Time Machine drive and re-mount it after you turn off Time Machine (see step 2).

If it still doesn’t work, try a reboot.

If it still still doesn’t work, try checking the “Erase destination” box in Disk Utility. This forces a block-level copy rather than just copying files.