title: Is it necessary to use three nodes to build RabbitMQ cluster?
body: <p>I have to say the official website provides very little information to understand RabbitMQ clearly.</p>
  <p>The official website suggests using three nodes to build a cluster. What is the reason for that? I suppose it's like ZooKeeper, which needs an odd number of nodes to do a quorum and elect the master.</p>
  <p>Also, what is the advantage of using a non-HA cluster? Improve the performance or what? If the node which a queue resides is down, then the queue is not working. So for all situation, is it necessary to set the cluster to be mirror queue and auto-sync?</p>