The short answer: Yes.
The long answer? If you want your Disc Publisher to perform to meet our high standards – fastest possible throughput, the fewest rejected discs, the most hands-free operation – then the second hard drive is needed. Use of an OS hard drive by the Operating System can be very frequent. If you have only a single hard drive, each time the hard drive is required for Operating System needs, then your Disc Publisher could potentially be waiting it’s turn to burn data from that drive. The result? Slower and more varied burn speeds, and the potential for duplication failure – in other words, the product that you are creating may not be the best that it can be.