We don’t recommend using SuperNZB with external disk drives or NAS drives (network attached storage).
SuperNZB is designed to be as fool-proof as possible from a novice user’s perspective. For example, suppose that the power goes off while SuperNZB is downloading an NZB file. When you re-start SuperNZB, it will look through your parts folder, and your downloads folder to see what’s there. It will then show all of those file totals on the Queue window, and you can resume downloading right where you left off. With a large NZB file that contains many thousands of files, such a feature can be a little time consuming. And if the files are not on your internal disk, it will take even longer.
SuperNZB is designed from the ground up with this kind of functionality, and as a consequence it is very resilient when things go wrong. And since NZB files are made by humans, there are plenty of things that can and will go wrong. So, SuperNZB is constantly reading and writing to-and-from your hard drive saving data, assembling parts, decoding, PAR-ing, RAR-ing, doing database look-ups, etc.
SuperNZB is very input/output intensive, so run it with your internal hard disk. Chances are that your internal drive is rather gigantic.
Of course, there is nothing wrong with wanting to store data on external devices. And we will keep this issue in mind even though SuperNZB itself cannot be easily redesigned for these scenarios. We have an as-yet unannounced NZB downloader in development aimed at advanced users, and we have support of non-internal drives as a design goal.