The progress of writing to HDFS is going as this image.

  • The HDFS Client requests to write a file block.
  • The NameNode responds to the Client with the DataNode to which to write the block.
  • The Client requests to write the block to the specified DataNode.
  • The DataNode opens a block replication pipeline with another DataNode in the cluster, and this process continues until all configured replicas are written.
  • A write acknowledgment is sent back through the replication pipeline.
  • The Client is informed that the write operation was successful.