Rymco,  The R710 will support a USB 2.0 compliant key. Which would be fast enough to have the Hyper-V core installed, and run from it. You can find information on the compatibly of the USB keys on page 9 of the "Getting Started" guide located here. Let me know if this helps answer your question.
Quick question... I can't find a spec on the internal USB of the R710.  Is it USB 2 or USB 3?  Would USB 2.0 be fast enough to install the parent Hyper-V Core on an internal USB drive?
PowerEdge R710 Internal USB