ioSafe N2: A Cornucopia of Functionality
See the full review of the ioSafe N2 Fireproof and Waterproof Dual-Drive NAS.
A NAS can do more than function as a backup. It can be a mail server, git or svn server, photo or video or iTunes or internet server, WIKI, Time Machine backup device and so on.
MPG has not tested these services, but these capabilities might be of interest in making a choice on a NAS which is more than file sharing and/or backup.