Data Disk Failure, Heartbeats and re-replication.

硬盘数据错误、心跳检测和重新复制。

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The advantage of replication is that reads are always local, as everybody has the data, and there is no re-balancing going on when a new node joins or an existing node leaves the cluster.

这种复制的优点在于它通常只在本地节点读取数据，因为每个节点都拥有这些数据；另外，当群集中有新节点加入或者需要移除现存节点的时候，它也不需要重新进行负载均衡。

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