Drivers are what instruct the operating system on how to use the device hardware.
Because the USB 3.1 protocol is supposed to be backward compatible with USB 3.0, a USB 3.1 capable USB hard drive should work with the My Cloud’s USB 3.0 port. However it would operate at USB 3.0 speed, not USB 3.1 speed. There are many complaints in this subforum of the USB 3.0 port on the My Cloud not providing true USB 3.0 speed. Rather the speed is significantly less than the USB 3.0 standard advertises.
If the USB drive is not being recognized, not being properly mounted, or the Dashboard indicates 0K, you can do a subforum search using the magnifying glass icon upper right to find numerous other threads that discuss these various problems that many others have experienced. Sometimes there may be a solution, other times not.
Here is one recent thread discussing various issues preventing a USB drive from being properly seen/mounted by the My Cloud:
http://community.wd.com/t/mycloud-4tb-cant-recognize-external-usb3-0-hdd/181050
