By Ashish Nadkarni (Linux Insider)
NAS islands today suffer from the "weakest link" phenomenon -- the least secure resource in the environment can be a gateway to a security nightmare. In a virtualized NAS environment, a single security policy can be applied to the entire environment, because all access is controlled via the virtualization appliance.

http://www.linuxinsider.com/story/GEu2UDU3JedkbU/A-Closer-Look-at-NAS-Virtualization.xhtml