流水线复制当某个客户端向HDFS文件写数据的时候，一开始是写入本地临时文件，假设该文件的replication因子设置为3，那么客户端会从Namenode获取一张Datanode列表来存放副本。

When a client is writing data to an HDFS file, its data is first written to a local file as explained in the previous section. Suppose the HDFS file has a replication factor of three.

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