四、高可用集群的分类     1.双机热备（Active/Passive） 官方说明：Two-node Active/Passive clusters using Pacemaker and DRBD are a cost-effective solution for many High Availability situations.

2.多节点热备（N+1） 官方说明：By supporting many nodes, Pacemaker can dramatically reduce hardware costs by allowing several active/passive clusters to be combined and share a common backup node.

3.多节点共享存储（N-TO-N） 官方说明：When shared storage is available, every node can potentially be used for failover. Pacemaker can even run multiple copies of services to spread out the workload.

4.共享存储热备 （Split Site） 官方说明：Pacemaker 1.2 will include enhancements to simplify the creation of split-site clusters.