We're starting to ramp up our Virtual Machine operations and are increasingly running more and more Windows guests. As far as I can tell traditional antivirus programs are not a scalable solution for large deployments because of the load they put on the guests and the storage while they're running. At best we would be able to get away with a couple of dozen Windows guests, running staggered scans at nights and on the weekend..
Most traffic to the Virtual Machines is in the form of email and remote desktop sessions - however, some people do map drives to the virtual machine to transfer files.
What is the best way to handle antivirus scanning for Virtual Machines in the general case? We're using RHEV so product specific options like vShield Endpoint aren't an option.