I really recommend that the drive have its own power source. Intensive disk access may expose weak port power

when you least want it.
That said, the 2 port USB cable.

And DON'T try any USB powered HD on a UNPOWERED hub. (The powered hub should have at least a 5V 2+ Amp supply. Each port can supply 1/2 amp, so multiply ports by .5 and the toss in an extra .5 for the Hub and losses)