SAV for NAS is not a product you install onto any NAS or SAN device. You install it onto a Windows, Linux or SPARC server and the NAS will have a product that sends file scan requests to the Scan Engine.
I did a quick google search for xsan and browsed through Apple's admin guide but I do not see any built-in support for a connector to send the requests to Scan Engine. If there is a third party program, then maybe that would work.
Perhaps you are meaning to post this in the Endpoint Protection forum? I do not know anything about that product so you would want to post there if you haven't already. From what I can see, the Xsan software just installs onto any server running Mac OS X Server so you may be able to use a product that installs onto the OS of the server like Endpoint for Mac.