Hadoop Distributed File System (HDFS) DATA-SCIENCE-OPTIMIZE Practice Questions (Page 3)

Questions 11–15

1. 11application · medium

   A web application running outside the Hadoop cluster needs to read a file from HDFS over HTTP. The application does not have the Hadoop client libraries installed. Which access method should the developer use?

   • AUse the WebHDFS REST API by sending an HTTP GET request to the NameNode's webhdfs endpoint.
   • BUse the hdfs dfs -cat command from the application's server.
   • CUse the Secondary NameNode's HTTP endpoint to read the file.
   • DUse the HDFS Java API by adding the hadoop-client dependency to the application.
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2. 12application · medium

   A client is writing a file to HDFS. The first DataNode in the write pipeline fails after receiving the first block. What happens to the write operation?

   • AThe client retries the write with a new DataNode, and the block is re-written from the beginning.
   • BThe block is written to the remaining DataNodes, and the replication factor is reduced.
   • CThe NameNode takes over the write and completes it on behalf of the client.
   • DThe write fails permanently and the client must restart the entire operation.
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4. 13foundation · easy

   Which HDFS shell command copies a file from the local filesystem into HDFS?

   • Ahdfs dfs -copyFromLocal /local/path /hdfs/path
   • Bhdfs dfs -get /local/path /hdfs/path
   • Chdfs dfs -rm /local/path /hdfs/path
   • Dhdfs dfs -ls /local/path /hdfs/path
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5. 14application · medium

   An HDFS administrator notices that a DataNode has reported a checksum error for a block. The block has a replication factor of 3. What will HDFS do to maintain data integrity?

   • AThe client will read the block from another replica and overwrite the corrupted replica in place.
   • BThe Secondary NameNode will restore the block from its last checkpoint.
   • CThe DataNode will delete the corrupted block and the NameNode will re-replicate it from a healthy replica.
   • DThe NameNode will immediately shut down the DataNode to prevent further corruption.
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6. 15application · easy

   A user wants to move a file from /data/raw/ to /data/processed/ in HDFS. The file is 500 MB. Which command should they use?

   • Ahdfs dfs -mv /data/raw/file.csv /data/processed/
   • Bhdfs dfs -put /data/raw/file.csv /data/processed/
   • Chdfs dfs -cp /data/raw/file.csv /data/processed/
   • Dhdfs dfs -rm /data/raw/file.csv /data/processed/
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