Summary: I initially had this setup for RAID1, with two Hitachi HDS724040ALE640 4TB drives. Since the rest of my drives are in back-order. I set this up in production, thinking I can expand later. Sure enough when the rest of my drives came; I was able to migrate from RAID1 to RAID 5, with a total of five drives. These are 4TB drives; the completion time was almost 20 hours. All of my iSCSI mounts, NFS share, was just temporarily offline, but they mounted automatically when done.
Summary: I live far away in middle east, and I find it important to mention that QNAP factory packing is more than excellent. Excellent product, easy to setup, and the sound of fan is not bad at all if the server is placed away from your screen. The two fans keeps running all the time, unless you do play with their running operation, which I didn't need to do. No heat at all coming out of the case.