1. A non-transitory computer readable medium comprising computer executable instructions which when executed by a computer cause the computer to perform the method of: merging, according to a plurality of merge rules: at least one target virtual disk descriptor that describes at least one virtual disk associated with an existing target virtual machine in a target virtualized environment; with: at least one source virtual disk descriptor that describes at least one virtual disk associated with a source; to obtain at least one merged virtual disk descriptor compatible with said target virtualized environment, said at least one merged virtual disk descriptor being compatible with a target hypervisor; and replacing said at least one virtual disk associated with said existing target virtual machine in said target virtualized environment with said at least one virtual disk associated with said source, in accordance with said at least one merged virtual disk descriptor, wherein at least one instance of said at least one virtual disk associated with said source executes on said target hypervisor according to said at least one merged virtual disk descriptor embodying said merge rules.