One of the cool features of Hyper-V is our built-in support for backing up running virtual machines with zero service downtime via VSS. The problem is that in order to fully utilize this functionality you need to have a backup program with specific support for Hyper-V.
Note, you can use the VSS backup capabilities “by hand” using the command line under Windows (as discussed here). You can also backup Hyper-V using Windows Server Backup by following the directions here – but in this case it is a simple “all or nothing” backup.
But now, with the release of Backup Exec 12.5, Symantec has added fully support for backing up Hyper-V and Hyper-V virtual machines. You can read more (as well as download a trial) here: http://www.symantec.com/business/products/newfeatures.jsp?pcid=pcat_storage&pvid=57_1