I purchased a netgear ready nv+ NAS for use in our practice with AC and it is working just fine. Two 500GB drives. can go up to 4 500GB drives and is hot swappable, RAID 0, 1, or 5. also, has XRAID and Flex-Raid options where you can add drive capacity if and when your database gets too big. This was better than the equivalent myworldbook and buffalo units but just a shade more expensive. Shopping on cnet.com I found one at securemart.com for about $1050.
