HDFS - Blockreport

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1 - About

A blockreport is a list of all HDFS data blocks that correspond to each of the local files, and sends this report to the NameNode.

Each datanode create and send this report to the namenode:

  • when the DataNode starts up (It scans through its local file system)
  • at specified interval ?

A Blockreport contains the list of data blocks that a DataNode is hosting. Each block has a specified minimum number of replicas.

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3 - Management

3.1 - Trigger a block report

with HDFS - DFSAdmin, see the options -triggerBlockReport [-incremental] <datanode_host:ipc_port>