(5) In HDFS (Hadoop DFS), applications create a new file by writing the data to it. Once the file is closed, the bytes cannot be modified or removed except the new data can be added to the file by reopening the file again. HDFS implements a singlewriter, multiple-reader model. Every time a node opens a file, it is granted a lease for the file, no other client can write to that file. A hit to the NameNode permits the lease to be extended. Once the lease expires and the file is closed, the changes are available to the readers.