A network partition can cause a subset of DataNodes to lose connectivity with the NameNode.

网络切割可能导致一部分Datanode跟Namenode失去联系。

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Finally, each cluster will have a single jobtracker that is responsible for scheduling work at the datanodes and a tasktracker per datanode that performs the actual work.

最后，每个集群有一个jobtracker，它负责调度datanode上的工作。每个datanode有一个tasktracker，它们执行实际工作。

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The NameNode detects this condition by the absence of a Heartbeat message. The NameNode marks DataNodes without recent Heartbeats as dead and does not forward any new IO requests to them.

Namenode通过心跳包的缺失检测到这一情况，并将这些Datanode标记为dead，不会将新的IO请求发给它们。

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