Similar to a rackmount server, a rackmount NAS will require a standard 19 inch or 23 inch server rack or cabinet. They can be found in the standard rack-mount form factors, including 1U, 2U, 3U, and 4U. For IT professionals that need more expandability, there are units up to 9U tall and with 50 hot-swappable drive bays. If you already have a server rack with available slots, a rackmount NAS storage solution is more space-efficient than a desktop NAS.