Your cluster has the following characteristics:
A rack aware topology is configured and on
Replication is not set to 3
Cluster block size is set to 64 MB
Which describes the file read process when a client application connects into the cluster and
requests a 50MB file?
A.
The client queries the NameNode which retrieves the block from the nearest DataNode to the
client and then passes that block back to the client.
B.
The client queries the NameNode for the locations of the block, and reads from a random
location in the list it retrieves to eliminate network I/O leads by balancing which nodes it retrieves
data from at any given time.
C.
The client queries the NameNode for the locations of the block, and reads all three copies. The
first copy to complete transfer to the client is the one the client reads as part of Hadoop’s
speculative execution framework.
D.
The client queries the NameNode for the locations of the block, and reads from the first location
in the list it receives.
Answer is “D”
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answer is A
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Namenode only provides block location to client, rest i/o operations on file are carried out by data nodes.
Correct answer is D
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answer is D as the list is sorted by distance from shortest to longest
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Correct answer is A
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