The initial unit I received through NewEgg was DOA. I had to send it back and get another. Perhaps if I hadn't already purchased the drives I would have gone with something else. Anyways, the new unit performed flawlessly. It has a built in web page for setup. Once it is attached to the network you type in the default IP address and up comes the configuration page. You format the drives and set up the RAID level. If I had chose not to use a RAID setup, I would have a 2Tb storage space.
I do not leave my unit powered on all the time. I do a weekly backup of my photo folders and Lightroom catalogs. I only power it up to do these backups. So far it has performed flawlessly. The unit is compact, as shown below.
NewEgg has a rebate on the DNS-321 currently. Today, I would probably go with 1.5Tb or 2.0Tb drives (Can you believe it?). To learn more about RAID levels click here.