CCA-410 · Question #72
When requesting a file, how does HDFS retrieves the blocks associated with that file?
The correct answer is D. the namenode reads the block ID's from disk. Here is how a client RPC request to the Hadoop HDFS NameNode flows through the NameNode. The Hadoop NameNode receives requests from HDFS clients in the form of Hadoop RPC requests over a TCP connection. Typical client requests include mkdir, getBlockLocations, create file, etc…
Question
When requesting a file, how does HDFS retrieves the blocks associated with that file?
Options
- Athe client polls the datanodes for the block ID's
- Bthe namenode requires the datanode for the block ID's
- CThe namenode reads the block ID's from memory
- Dthe namenode reads the block ID's from disk
How the community answered
(23 responses)- A4% (1)
- B9% (2)
- C13% (3)
- D74% (17)
Explanation
Here is how a client RPC request to the Hadoop HDFS NameNode flows through the NameNode. The Hadoop NameNode receives requests from HDFS clients in the form of Hadoop RPC requests over a TCP connection. Typical client requests include mkdir, getBlockLocations, create file, etc. Remember - HDFS separates metadata from actual file data, and that the NameNode is the metadata server. Hence, these requests are pure metadata requests - no data transfer is
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