Mariadb Galera Cluster

MHA架构是通过在节点折腾二进制日志文件与中继日志文件，进而通过脚本来控制切换。

Galera Cluster

Galera优势：

> True Multi-master Read and write to any node at any time.
      # 任何时间任何节点都可以读写(并不代表写分摊，底层复制也会有些IO)
> Synchronous Replication No slave lag, no data is lost at node crash.
      # 同步复制没有数据延迟(滞后)，节点奔溃也不会丢失数据
> Tightly Coupled All nodes hold the same state. No diverged data between nodes allowed.
      # 所有节点都有相同耦合状态，节点之间不允许数据有偏差
> Multi-threaded Slave For better performance. For any workload.
      # 多线程有更好的性能，适合任何负载
> No Master-Slave Failover Operations or Use of VIP.
      # 不存在主从故障迁移操作，或者使用虚拟IP
> Hot Standby No downtime during failover (since there is no failover).
      # 热备，无故障转移时间，(由于没有故障转移)
> Automatic Node Provisioning No need to manually back up the database and copy it to the new node.
      # 新节点数据自动完成复制，无需手动备份，复制数据到新节点(添加集群节点，底层wsrep协议自动完成数据复制)
> Supports InnoDB.
      # 支持InnoDB存储引擎
> Transparent to Applications Required no (or minimal) changes) to the application.
      # 无需改变应用，对于应用程序是透明的
> No Read and Write Splitting Needed.
      # 无需读写分离

galera_cluster.png