NameNode and DataNode roles in Hadoop - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the primary role of the NameNode in Hadoop?

The NameNode manages the metadata of the Hadoop file system. It keeps track of the file system tree and the locations of all the data blocks on DataNodes.

beginner

What does a DataNode do in Hadoop?

A DataNode stores the actual data blocks in the Hadoop file system. It handles read and write requests from clients and reports the status of data blocks to the NameNode.

intermediate

How do NameNode and DataNode work together?

The NameNode keeps metadata and directs where data is stored. DataNodes store the data blocks and send reports to the NameNode. Together, they manage data storage and retrieval efficiently.

intermediate

Why is the NameNode considered a single point of failure in Hadoop?

Because the NameNode holds all metadata and controls the file system, if it fails, the whole Hadoop cluster cannot function properly until it is restored or a backup takes over.

intermediate

What kind of data does the DataNode report back to the NameNode?

DataNodes send heartbeat signals and block reports to the NameNode. These reports include information about the health and status of data blocks stored on them.

What is stored by the NameNode in Hadoop?

A Metadata about files and directories

B Actual data blocks

C User login information

D Network configuration

The NameNode stores metadata such as the file system tree and block locations, not the actual data.

Which component stores the actual data in Hadoop?

A DataNode

B JobTracker

C ResourceManager

D NameNode

DataNodes store the actual data blocks in the Hadoop file system.

What happens if the NameNode fails?

A Data is lost permanently

B DataNodes continue working normally

C The Hadoop cluster stops functioning properly

D New data is automatically stored elsewhere

Since the NameNode manages metadata, its failure causes the cluster to stop functioning until recovery.

How do DataNodes communicate their status to the NameNode?

A By updating the file system tree

B By running MapReduce jobs

C By storing metadata locally

D By sending heartbeat signals and block reports

DataNodes send heartbeat signals and block reports to inform the NameNode about their health and data status.

Which of the following is NOT a role of the NameNode?

A Managing file system metadata

B Storing actual data blocks

C Directing DataNodes where to store data

D Maintaining the file system namespace

The NameNode does not store actual data blocks; that is the role of DataNodes.

Explain the roles of NameNode and DataNode in Hadoop and how they work together.

Think about who keeps track of data and who holds the data.

Why is the NameNode considered a critical component in Hadoop's architecture?

Consider what happens if the NameNode stops working.