<P> Restoring a snapshot consists of discarding or disregarding all overlay layers that are added after that snapshot, and directing all new changes to a new overlay . </P> <P> The snapshots described above can be moved to another host machine with its own hypervisor; when the VM is temporarily stopped, snapshotted, moved, and then resumed on the new host, this is known as migration . If the older snapshots are kept in sync regularly, this operation can be quite fast, and allow the VM to provide uninterrupted service while its prior physical host is, for example, taken down for physical maintenance . </P> <P> Similar to the migration mechanism described above, failover allows the VM to continue operations if the host fails . However, in this case, the VM continues operation from the last - known coherent state, rather than the current state, based on whatever materials the backup server was last provided with . </P> <P> A video game console emulator is a program that allows a personal computer or video game console to emulate a different video game console's behavior . Video game console emulators and hypervisors both perform hardware virtualization; words like "virtualization", "virtual machine", "host" and "guest" are not used in conjunction with console emulators . </P>

Another name for a virtualization server is a