Recent release of Service Pack 1 for Microsoft Virtual Server 2005 R2 introduces capability to perform virtual machines live back through Volume Shadow Service (VSS) feature included in Windows Server 2003 hosts.
Unfortunately, as virtualization.info exposed during Service Pack 1 beta program, this capability cannot be leveraged by NTBackup included in every Windows edition, but users need 3rd party backup solutions.
Anyway Microsoft customers can obtain virtual machines live backup as well without buying 3rd party solutions, but just using upcoming Data Protection Manager (DPM) 2007, which further complicates company position on this issue.
Technical steps to integrate Virtual Server 2005 R2 SP1 and DPM 2007 are now detailed in a new webcast Microsoft arranged for June 21.
Register for it here.