A:Answer You Can Definitely Have More Than One (1) External HD' Depending On How Many USB Ports U Have On Your PC. You Can Also Ad A USB Hub To One Of Your USB Ports To Add More USB Ports. As Far As Auto BackUp To Another Portable. You Will Have To Have A BackUp Program That Supports "Mirroring", Which Would Automatically RollOver To Another Drive Should One Of Your Portables Become Full.
Hope This Helps.