I am having the similar issue. I have an older Time capsule 802.11n, 500 gb hard drive. It does not have a firewire port, but only ethernet or USB available. I bought a new G-raid external 4tb hard drive to add, but the time machine will not recognize the G-raid that is mac formatted via the usb port. Is it because of the usb or is the time machine to old to work with this external hard drives? If I plug the graid directly to my computer (macbook pro working on OS 10.5.8) I can see it, but can't get the time machine to use it as an extra drive during auto back up. When I double click on the G-raid icon on my computer it just opens like any folder & does not ask for an set up.
Am I dreaming, or can I make these multi-generational products work together?
That drive should be usable that way, but may require a powered USB hub. The port on the TC is vastly underpowered; most self-powered drives will work without help, but some of the larger ones won't.
There's nothing in any Apple tech articles, but I've read that a partition over about 2.2 GB either may not be recognized on the TC or you may only be able to use the first 2.2 GB or so.
Try a powered hub; if that doesn't work, try spliting the HD into 2 partitions (connect directly to your Mac to do that) and see if it's recognised that way, with the powered hub. If not, there may be a problem with the port or other innards of the TC.
Note that backups can't "span" from the TC's HD to another volume; for any one Mac, you can back up to either the TC's internal HD or the external HD (unlike the TC's internal HD, you can partition the external).
When connected to the TC, it should show up in Airport Utility something like this (a 500 GB Seagate with 6 partitions):
EDIT: Be sure the drive is formatted for a Mac -- any variant of Mac OS Extended.
Message was edited by: Pondini