I'm struggling right now trying to figure out what to do about increasing my NAS storage. It's either replace every 2GB drive in my current 6-drive RNP with 3GB models, or buy another enclosure and add a few 3 or 2TB drives to that. I'm leaning toward the new enclosure because upgrading drives in the original from 2 to 3 doesn't give you much extra storage and has an extremely high cost per TB - unless I can re-sell the original 2TB drives to offset the cost.

With double drive redundancy in my setup, I have to upgrade at least 3 drives before I see even an additional byte of storage.