Which among the following are the duties of the NameNodes

manage file system namespace
it is responsible for storing actual data
perform read-write operation as per request for the clients
none of the above

The correct answer is A.

The NameNode is the master server in a Hadoop Distributed File System (HDFS). It manages the file system namespace and regulates access to files by clients. It does not store actual data, which is stored in DataNodes. It also does not perform read-write operations on behalf of clients.

The NameNode is a critical component of HDFS and its failure can cause the entire system to become unavailable. It is typically deployed on a highly available cluster of machines to ensure that it is always available.

Here is a brief explanation of each option:

  • Option A: The NameNode manages the file system namespace. This means that it keeps track of all the files and directories in the HDFS, as well as their locations on the DataNodes.
  • Option B: The DataNodes are responsible for storing actual data. They do this by replicating the data across multiple nodes in the cluster.
  • Option C: The NameNode does not perform read-write operations on behalf of clients. This is done by the DataNodes.
  • Option D: None of the above is correct.