Do you show any errors on the SAN side? is it dropping the luns due to too much data change or a journal getting full? If it happens after some time, i doubt it would be something like a shutdown trigger... if the SAN was recently changed, I'd look at what they're doing. Do you have the option at least to add a physical drive to the server to get a good backup going? maybe see if backing up to a physical drops you or not (if one is easy to obtain)