Yes. I've tried loads of portable HD's and none work without a power supply. Also anyone know if a Y Cable will work on the front 2 ports as well? Cuz I'd like to have an HD plugged into the back for Wiiu games and a Y Cable infront for vWii. And what's the name again of that app that'll let ya have 2 USB's plugged in and not be forced to manage?
think it's ustealth: https://gbatemp.net/threads/ustealth-wii-u-format-disk-nag-workaround.352786/ I'm using a toggle switch with mine though. I'm also using cfg usb loader.