'Changes the number of replicas in this ring.
If the new replica count is sufficiently different that
self._replica2part2dev will change size, sets
self.devs_changed. This is so tools like
bin/swift-ring-builder can know to write out the new ring
rather than bailing out due to lack of balance change.'

def set_replicas(self, new_replica_count):

    old_slots_used = int((self.parts * self.replicas))
    new_slots_used = int((self.parts * new_replica_count))
    if (old_slots_used != new_slots_used):
        self.devs_changed = True
    self.replicas = new_replica_count
