Practice Library
All MCQs
Browse exam-wise, subject-wise, and country-wise MCQs with explanations.
Choose an option to check your answer.
Correct Answer: A. A temporary state in which namespace changes are restricted while block status is assessed
Explanation:
At startup, the NameNode waits for enough block reports and replicas.
It exits safe mode when the file system is considered sufficiently available.
Choose an option to check your answer.
Correct Answer: D. Detecting data corruption during storage or transfer
Explanation:
Checksums allow clients and DataNodes to verify block integrity.
Corrupt replicas can be replaced from healthy copies.
Choose an option to check your answer.
Correct Answer: C. It prefers a nearby replica to reduce network cost
Explanation:
Topology-aware selection can favor local or same-rack copies.
This improves throughput and reduces cross-rack traffic.
Choose an option to check your answer.
Correct Answer: B. A chain of DataNodes through which a block and its replicas are written
Explanation:
The client sends packets to the first DataNode, which forwards them along the pipeline.
Acknowledgments flow back after replicas receive the data.
Choose an option to check your answer.
Correct Answer: A. Obtaining block locations from the NameNode and reading data directly from DataNodes
Explanation:
The NameNode supplies metadata rather than streaming user data.
The client contacts suitable DataNodes for each block.
Choose an option to check your answer.
Correct Answer: D. Using multiple independent NameNodes to manage separate namespaces
Explanation:
Federation scales namespace capacity and isolates workloads.
The DataNodes can store blocks for multiple block pools.
Choose an option to check your answer.
Correct Answer: C. Using active and standby NameNodes to reduce namespace-service downtime
Explanation:
A standby NameNode maintains synchronized metadata and can take over.
Shared edits and failover coordination support continuity.
Choose an option to check your answer.
Correct Answer: B. Periodically creating namespace checkpoints
Explanation:
The Secondary NameNode merges the fsimage and edit log.
Its name is misleading because it was not simply an automatic backup NameNode.
Choose an option to check your answer.
Correct Answer: A. To merge the fsimage with accumulated edit-log changes
Explanation:
Checkpointing limits edit-log growth and speeds future NameNode recovery.
It does not replace block replication.
Choose an option to check your answer.
Correct Answer: D. A persistent snapshot of the file-system namespace
Explanation:
The fsimage stores namespace metadata at a point in time.
It is combined with edit-log entries during NameNode startup.
Choose an option to check your answer.
Correct Answer: C. A record of changes made to the file-system namespace
Explanation:
Namespace operations are written to the edit log for durability.
They are later merged with the namespace image during checkpointing.
Choose an option to check your answer.
Correct Answer: B. File and block metadata are kept primarily in memory for fast access
Explanation:
Metadata memory limits the practical number of files and blocks.
This is one reason small files can be problematic.
