Xsan 2 unmount volume due to no internet connection?

One of your ethernet connections is required for metadata communication. If you drop this connection, you drop the SAN volume. In an ideal setup, you are running two networks. A data network which is your primary network and handles your web, email, file sharing, etc., and a second private network just for the metadata traffic. While you can run metadata and data over the same connection, this is generally discouraged as your primary data network ends up being too chatty with bonjour, netware, and other broadcast protocols.

Internet, no. But metadata yes. You are saying that when the primary network is down you are dropping the volume?

Are you sure that you have the Xsan client using the correct network for metadata? I've seen some environments in which even though a private network was built, the software was configured to use the primary network for metadata.

Any logging information available when the volume goes down?