Certified Data Professional (CDP)

The client asks NameNode where the block is located (s). The NameNode gives the client the block location(s) back. Data is immediately read by the client from the DataNode (s) The client simultaneously requests every DataNode. The client receives a response from the DataNode with the requested data. Data is immediately read by the client from the DataNode. For the block location, the Client contacts the NameNode (s). The NameNode contacts the DataNode that contains the desired data block. Data is exchanged from the DataNode to the NameNode to the Client from the NameNode to the Client. For the block location, the client contacts the NameNode (s). The NameNode then requests block locations from the DataNodes. The NameNode leads the client to the DataNode, holding the requested data block when the DataNodes react to it (s). Data is then read directly from the DataNode by the client.