'Backup an instance on this host.
:param backup_type: daily | weekly
:param rotation: int representing how many backups to keep around'

@wrap_exception()
@reverts_task_state
@wrap_instance_fault
def backup_instance(self, context, image_id, instance, backup_type, rotation):

    self._do_snapshot_instance(context, image_id, instance)
    self._rotate_backups(context, instance, backup_type, rotation)
