This feature, first available in vSphere 4, provides the foundation for incremental (or differential) backup of virtual disks. Your application can back up only changed data as indicated by the

QueryChangedDiskAreas

method. Virtual machines with virtual hardware version 7 and later support changed block tracking. These virtual machines contain

changeTrackingSupported

in the

capability

field of the

VirtualMachine

managed object. See Changed Block Tracking on Virtual Disks for details.