FUNDAMENTALS OF COMPUTER

Detailed explanation-1: -In Read-Write operation client first, interact with the NameNode. NameNode provides privileges so, the client can easily read and write data blocks into/from the respective datanodes.

Detailed explanation-2: -To write a file inside the HDFS, the client first interacts with the NameNode. NameNode first checks for the client privileges to write a file. If the client has sufficient privilege and there is no file existing with the same name, NameNode then creates a record of a new file.

Detailed explanation-3: -Answer: The client reading the data from the HDFS filesystem in Hadoop gets the block location from the Namenode and then gets the data from the Datanode.

Detailed explanation-4: -When a user wants to read a file, the client will talk to namenode and namenode will return the metadata of the file. The metadata has information about the blocks and their locations. When the client receives metadata of the file, it communicates with the datanodes and accesses the data sequentially or parallelly.