facility for using images created by backup software to recreate an entire machine as it was at the point in time in the past when the backup was taken . the facility can be extended so as to bring up a set of machines which together serve some logical business function as in a cluster or federated servers , and further extended so that an entire data center may be virtualized from backup images . the virtualized servers provided may serve as an alternate data center standing in case of disaster or to meet maintenance windows achieving low cost instant disaster recovery . a set of virtual machines may stand in for physical machines for a period of time and then resynchronized or re - seeded to physical machines via a combination of bare metal recovery and re - synchronizing from live lxjns that form the virtual machine disks .