There is one extra USB port on the DS101. On rev 2.2 of the hardware there's already a connector so you can just solder on a header and use it. On rev 3.0, you'll have to do some neat soldering to get it to work.
The header on rev2.2 is all the way up in the left corner of the PCB, where there's space for a fan. On rev3.0, the port has to be taken from R15 and R16, and you'll have to connect GND and VBus from elsewhere. I pulled VBus from the drive power connector, and GND from a screwhole. Solder the wires from the USB-Controller side of R15 and R16.