MCQs on HDFS Data Management | Hadoop HDFS
Delve into HDFS Data Management with 30 carefully designed MCQs, covering data placement policy, load balancing with HDFS balancer, DataNode capacity and health, and HDFS file block management techniques.
1. HDFS Data Placement Policy
- What is the default HDFS data placement policy?
- A) All blocks on a single node
- B) Random placement across all nodes
- C) First replica on the writer’s node, others on different racks
- D) Equal distribution across all racks
- Why does HDFS use a rack-aware placement policy?
- A) To improve data locality
- B) To increase fault tolerance by spreading data across racks
- C) To reduce disk usage
- D) To minimize metadata storage
- How many replicas of a data block are typically stored in HDFS?
- A) 1
- B) 2
- C) 3
- D) 4
- In a multi-rack HDFS cluster, where is the third replica of a data block typically stored?
- A) On the same node as the first replica
- B) On the same rack as the first replica
- C) On a different rack from the first two replicas
- D) Randomly across the cluster
- What is the primary goal of the HDFS data placement policy?
- A) Minimizing storage costs
- B) Maximizing data security
- C) Ensuring fault tolerance and data reliability
- D) Reducing metadata storage requirements
2. HDFS Balancer for Load Balancing
- What is the purpose of the HDFS Balancer?
- A) To manage metadata updates
- B) To rebalance data blocks across DataNodes for even utilization
- C) To replicate blocks across clusters
- D) To optimize network performance
- When is the HDFS Balancer typically used?
- A) When a DataNode fails
- B) When the NameNode becomes overloaded
- C) When there is an imbalance in DataNode storage utilization
- D) When a new block is added
- How does the HDFS Balancer identify underutilized DataNodes?
- A) Based on the number of blocks stored
- B) By analyzing block replication factor
- C) By comparing the storage utilization of DataNodes
- D) By monitoring network traffic
- Which command is used to start the HDFS Balancer?
- A)
hdfs balancer -start - B)
hdfs dfsadmin -balancer - C)
start-balancer - D)
hdfs balancer -execute
- A)
- What happens to the cluster during the HDFS Balancer process?
- A) Data is deleted from overutilized nodes
- B) Data blocks are moved from overutilized to underutilized DataNodes
- C) Metadata is replicated across the cluster
- D) The cluster stops accepting new data
3. DataNode Capacity and DataNode Health
- How is the capacity of a DataNode calculated?
- A) By counting the number of files stored
- B) By summing up the disk space available across all disks on the node
- C) By measuring the network throughput of the node
- D) By calculating the average size of data blocks
- What is a sign of an unhealthy DataNode?
- A) High storage capacity
- B) Frequent heartbeats to the NameNode
- C) Missing block reports
- D) Excessive network usage
- What is the role of heartbeats in DataNode health monitoring?
- A) To update the block metadata
- B) To confirm the DataNode is active and operational
- C) To replicate blocks to other nodes
- D) To check storage utilization
- What action does the NameNode take if a DataNode stops sending heartbeats?
- A) It ignores the DataNode until it restarts
- B) It replicates the missing blocks to other nodes
- C) It deletes the blocks stored on the DataNode
- D) It shuts down the cluster
- Which command can be used to check the status of a DataNode?
- A)
hdfs dfsadmin -report - B)
hdfs datanode -status - C)
hdfs nodemanager -status - D)
hdfs healthcheck
- A)
4. HDFS File Block Management and Optimization
- What is a file block in HDFS?
- A) A collection of files stored together
- B) A fixed-size unit of data into which files are split
- C) A container for metadata
- D) A logical partition of the file system
- What is the default block size in HDFS?
- A) 64 MB
- B) 128 MB
- C) 256 MB
- D) 512 MB
- How does block replication improve fault tolerance?
- A) By storing each block on a single node
- B) By copying blocks across multiple nodes and racks
- C) By compressing data
- D) By encrypting blocks
- What is the benefit of increasing the block size in HDFS?
- A) Reduced storage utilization
- B) Faster access to small files
- C) Improved performance for large file reads
- D) Increased block replication
- How can administrators optimize file block placement in HDFS?
- A) By using custom replication factors
- B) By storing all blocks on a single rack
- C) By reducing the block size
- D) By disabling replication
- Which tool is used to remove corrupted or incomplete blocks from HDFS?
- A)
hdfs balancer - B)
hdfs dfsck - C)
hdfs cleanup - D)
hdfs admin
- A)
- What is the effect of storing many small files in HDFS?
- A) Improved performance
- B) Increased memory usage on the NameNode
- C) Reduced fault tolerance
- D) Faster replication
- How does HDFS handle file block failures?
- A) By ignoring the block
- B) By replicating the block from another node
- C) By deleting the file
- D) By stopping the cluster
- Which HDFS command is used to list the blocks of a file?
- A)
hdfs dfs -ls - B)
hdfs dfs -stat - C)
hdfs fsck - D)
hdfs dfs -blocks
- A)
- What happens when the replication factor for a file is increased?
- A) New replicas are created and stored on additional DataNodes
- B) The original blocks are moved to different racks
- C) The file is compressed
- D) No changes occur
Answers Table:
| Qno | Answer |
|---|---|
| 1 | C) First replica on the writer’s node, others on different racks |
| 2 | B) To increase fault tolerance by spreading data across racks |
| 3 | C) 3 |
| 4 | C) On a different rack from the first two replicas |
| 5 | C) Ensuring fault tolerance and data reliability |
| 6 | B) To rebalance data blocks across DataNodes for even utilization |
| 7 | C) When there is an imbalance in DataNode storage utilization |
| 8 | C) By comparing the storage utilization of DataNodes |
| 9 | B) hdfs dfsadmin -balancer |
| 10 | B) Data blocks are moved from overutilized to underutilized DataNodes |
| 11 | B) By summing up the disk space available across all disks on the node |
| 12 | C) Missing block reports |
| 13 | B) To confirm the DataNode is active and operational |
| 14 | B) It replicates the missing blocks to other nodes |
| 15 | A) hdfs dfsadmin -report |
| 16 | B) A fixed-size unit of data into which files are split |
| 17 | B) 128 MB |
| 18 | B) By copying blocks across multiple nodes and racks |
| 19 | C) Improved performance for large file reads |
| 20 | A) By using custom replication factors |
| 21 | B) hdfs dfsck |
| 22 | B) Increased memory usage on the NameNode |
| 23 | B) By replicating the block from another node |
| 24 | C) hdfs fsck |
| 25 | A) New replicas are created and stored on additional DataNodes |