The T8 has 3 USB sockets.
My 120Gb ("CBA Digital" identifies as USB2SATA Bridge under Windows) external hard drive requires both USB plugs to be attached (as
@james mc mentioned, some drives come with a USB lead that has a mini USB plug at one end, a normal USB plug at the other (for data and power) and a 2nd plug that can be used (just has power pins wired up)). See
http://www.amazon.co.uk/Nexons-USB-2-0-Cable-Mini-B/dp/B003N8HVQC for an example. If your hard drive has the newest micro USB type connection (normal micro USB with a bit on the left added on for USB3) then
http://www.amazon.co.uk/Storite-SuperSpeed-Seagate-Toshiba-External-BLACK/dp/B00IP8QIUK/ might help.
This particular drive seems to require a little more than 500mA sometimes, though the steady draw is more like 250mA. I've measured (using
https://www.amazon.co.uk/gp/product/B00JIFMXSK/ ) the output on the T8's USB sockets, and it seems to max out at around 480mA. Once this specific drive has spun up, I've noticed you can then unplug the second USB connection, perhaps the biggest power draw is spinning the platters up to speed?
We can't 100% guarantee compatibility as we don't have the drive (exact model??), but you should be OK. If you have problems, you could either use a mains-powered USB hub connected to your T8, or see if you can grab a lead that would allow you to use two USB plugs for extra power.