Is there a list of compatible USB drives for a ReadyNas Duo?

If I'm seeing suspect information in three threads why not ask in all three? People who read only one of the other two threads may be led to believe it will work when in this thread there's an example where it won't. Before posting I did a search and found a number of threads where the same question was asked but the poster was left hanging, the question never answered. I need to back this up, so just need good information before I buy another external drive that won't work. And if the problem has a solution I'll be happy to post it in those other threads as well, so anyone else researching the same or similar problem will find an answer.

Yes, I tied it both with a standard USB cable, one of those two-USB on one end cables for older drives that needed more power, and also a powered USB hub, it isn't recognized in any configuration. I can plug in two other (smaller) external laptop drives in generic cases and they're both recognized, so it isn't bad ports. It's an earlier Duo v1, not a v2.