CDP (Big Data Hadoop Administrator) 5

Question 1

A cluster shows that one DataNode's disk usage is at 95% while others are at 40%. Which parameter controls the threshold at which a DataNode is considered full and stops accepting new blocks?

Accepted Answer

dfs.datanode.du.reserved

Answer

dfs.datanode.du.reserved reserves a fixed number of bytes on each DataNode volume so the node stops accepting blocks before the disk is completely full.

Question 2

Which Hadoop service provides a REST gateway for interacting with HDFS from non-Java clients?

Accepted Answer

WebHDFS / HttpFS

Answer

WebHDFS is built into the NameNode and exposes an HTTP REST API; HttpFS is a standalone proxy offering the same API with better firewall-friendliness.

Question 3

In HDFS, what is a 'rack-aware' block placement policy designed to achieve?

Accepted Answer

Balancing fault tolerance and bandwidth by spreading replicas across racks

Answer

Rack-aware placement puts one replica locally, one on a different rack node, and one more on that second rack so a single rack failure doesn't lose data.

Question 4

Which command forces the NameNode to exit safe mode immediately without waiting for the threshold to be met?

Accepted Answer

hdfs dfsadmin -safemode leave

Answer

hdfs dfsadmin -safemode leave forces the NameNode out of safe mode regardless of whether the minimum replication threshold has been satisfied.

Question 5

What is the role of the HDFS Checkpoint Node (formerly Secondary NameNode)?

Accepted Answer

Periodically merging the fsimage and edit log to create a new checkpoint

Answer

The Checkpoint Node (Secondary NameNode) regularly combines the current fsimage and accumulated edits into a new fsimage, preventing the edit log from growing indefinitely.

CDP - Certified Data Professional Practice Test

CDP - Certified Data Professional Practice Test

CDP (Big Data Hadoop Administrator) 5