On a cluster running MapReduce v2 (MRv2) on YARN, a MapReduce job is given a directory of 10
plain text as its input directory. Each file is made up of 3 HDFS blocks. How many Mappers will
run?
A.
We cannot say; the number of Mappers is determined by the RsourceManager
B.
We cannot say; the number of Mappers is determined by the ApplicationManager
C.
We cannot say; the number of Mappers is determined by the developer
D.
30
E.
3
F.
10
should not it be F … since there are 10 files it would start 10 map tasks.
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Answer is “D”.
10 files x 3 blocks = 30 blocks.
Number of Mappers (in YARN) = number of input splits (in this case blocks) = 30
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Answer is D (30)
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D
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30 mappers
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Correct answer is E
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