In an email to support we were asked “If using multiple USB devices (ie a USB harddrive for backup or addition storage) changes the iPod drive assignment do you have to go through setup again?”
The answer:
No. No setup is required for the iPod or, for that matter, the Keypad Hub that interfaces our Keypads to the server using a USB port. CasaTunes automatically finds them, no matter what other USB devices are plugged in or unplugged during operation.

The Keypad Hub (and iPod) can also be used with USB Hubs to expand the quantity of USB ports, if you don’t have enough ports. The USB Hub should be powered to supply our Keypad Hub or the iPod with enough power. The Keyapd Hub requires less than 200 ma from the USB port when all six Keypads are plugged in and active.