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How NameNode tackle Datanode failures in Hadoop?

Answer Posted / Neeraj Rastogi

When a DataNode fails, the NameNode notices the absence of its heartbeats and marks the affected blocks as missing. The NameNode then schedules replication of these blocks to other available DataNodes. If necessary, the NameNode may also redirect client read and write requests to other DataNodes that have replicas of the desired data.

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