Hey all! Just thought I'd share this tidbit of information for those that are curious.
I have an HDD attached to my TC for use with Time Machine (the internal is being used as storage) and figured I'd connect it directly to my MB since I'm in the process of moving and really needed to back up while my TC was packed away. I was expecting TM to start a new backup on the hard drive since it's not possible to continue a backup when you switch the drive to a TC or AEBS... but I was pleasantly surprised when it continued backing up to my sparsebundle file while directly attached!
If only it were possible to continue a backup on a hard drive when you switch it to a base station...
There's kind of a way to do this actually, only downside is you need a second USB drive to do this. Big enough partitions would probably also work, but that will get tricky.
Set up your Mac to do one small Backup on the network shared drive. Just excclule most folders (also exclude system folders) so that the initial backup will complete quickly. Then, turn off Time Machine.
Your network shared drive now has a sparsebundle file in its root. this is actually not a file, it's a bundle with the real files in it. Time Machin mounts and unmounts this bundle every time it does backups over the network, it then appears just like any other volume.
Now you're thinking, you can just mount the sparsebundle and copy the folders of your old, USB attached Time Machine drive inside the bundle. Don't do this, Time Machine won't recognize those folders because there are some extra invisible files that contain the data Time Machine uses to know what files are there, when they were backed up, etc. Using terminal commands, you can actually copy those files over, too and correct their permissions...
But here's the simple way. Download SuperDuper (free version is fine for this purpose). Don't use Disk Utility, it does some small things differently and it won't all work as expected in the end. You're going to make an exact copy of the Time Machine drive inside the sparsebundle on the network shared drive. To make the copying faster, don't do it over the network (except if you have Gigabit Ethernet and decent cables), attach the shared drive to your Mac directly, using the fastest available. Connection.
Here's the connections sorted by speed for this scenario:
Gigabit Ethernet > Firewire 800 > Firewire 400, USB2.0 > 100MB Ethernet > 802.11n WIFI, 802.11g WIFI.
Not that Macs have an internal USB HUB, so copying data from one USB drive to another USB drive is slow because they're need to share the bandwidth. If one of the drives has Firewire, use that.
Once both your drives are connected properly, launch SuperDuper and select your old Time Machine Drive as source (drag and drop the drive icon) and use the sparsebundle as destination. Copy using "Backup - all files". Super Duper will take care of copying the invisible system files and keeping the permissions in order. If it refuses to copy because you don't have permissions on the sparsebundle, do "get Info" on the sparsebundle and give yourself read-write persmissions on it. Chances are, you're using different credentials when accessing the drive over the network than logging in on your Mac.
Once it's done copying, don't reactivate Time Machine yet. Try out if the backup really works. Reboot your Mac from the Leopard install Disc (hold "C" after the chime and it will boot from the DVD). Exit the Leopard installer and open Disk utility from the menu bar. Now click on the "Restore" tab and drag the sparesbundle into "source". If this doens't give you an error, you should be fine. Reboot normally and mabye let Disk Utility "Verify Disk" on the sparse bundle, this only takes a few minutes.
Once that is all done, reconect the new drive with the sparsebundle to the network share and pont Time Machine to that disc again. You should now be able to browse your old through the network.
More info:
http://discussions.apple.com/thread.jspa?threadID=1449878
