So you can let them share the disk or a partition. If you're backing-up multiple Macs to the same drive, you can make one partition for each, but it's not as helpful on a network drive, because each Mac's backups will be in a separate sparse bundle. That's highly recommended if you're going to be putting other data there, so the backups don't completely fill the disk (and be aware that Time Machine cannot back up that 'other' data.
Unlike the Time Capsule's disk, you can partition the USB drive. See the discussion in the pink box of Time Machine FAQ #5). (You can use the procedure in item #A8 to change that if desired, by cancelling the first backup as soon as the sparse bundle is created. Note, however, that it doesn't matter whether you use the Mac OS Extended (Journaled) or Mac OS Extended (Case-sensitive, journaled) Format, since Time Machine will put your backups in a case-sensitive sparse bundle.
If you use a large bus-powered drive, or want to connect multiple drives or printers, you'll need a powered USB hub, as the USB port is under-powered.īut first, connect the drive directly to your Mac, and erase and format it per the instructions in Time Machine FAQ #5. Mostly the same way you set it up to use the Time Capsule's internal HD.