Use a network Time Machine drive locally I typically backup over a network to a networked hard drive on another machine. For some unknown reason, backups tend to get incredibly slow over the network (the first few backups work fine and timely, then it gets crazy slow.) I let the backup run over gigabit for a night, and I came back to find 300 MB of 10 GB backed up.  Anyway...

I'd like to plug that networked HD into my notebook over FireWire directly, and backup to it's sparsebundle locally.  I tried mounting the sparsebundle (which was successful-- I see the past backups), but I can't select it as my backup volume in Time Machine preferences. It would seem I either need to:


Trick OS X into letting me backup to the sparseimage as a volume.
Trick OS X into connecting to my external firewire drive at afp://localhost/Drive/


Any other suggestions are more than welcome, but those seem to be the most logical options.  It's worth noting 1 isn't easy because TM doesn't want to backup to sparse disks.  2 isn't easy because AFP can't connect to localhost, it just tells you to access the shared files locally.

Suggestions appreciated!  Thanks.
You can try mounting that volume and then use the tmutil command to tell Time Machine where do you want backups to go to. Just make sure that nobody else is using the sparsebundle from the network

Stepwise:


Mount the .sparsebundle disk image
Open Terminal
In the Terminal command line, type:

sudo tmutil setdestination /Volumes/{mounted-disk-image}


Be sure to replace {mounted-disk-image} above to the drive's mount point name.
Open the Time Machine menu and force-start a backup.


Watch the contents of the Backups.backupdb folder in the disk image as Time Machine runs and ensure that it is creating your new backup set.

Note that you'll need Lion for this. Enter the command man tmutil in the Terminal for more information.