Question

Point out the correct statement.

(a) The number of sorted map outputs fetched into memory before being merged to disk

(b) The memory threshold for fetched map outputs before an in-memory merge is finished

(c) The percentage of memory relative to the maximum heap size in which map outputs may not be retained during the reduce

(d) None of the mentioned

I had been asked this question during an online exam.

I need to ask this question from MapReduce Features topic in portion Developing a MapReduce Application of Hadoop

Answer 1

The correct choice is (a) The number of sorted map outputs fetched into memory before being merged to disk

Easiest explanation: When the reduce begins, map outputs will be merged to disk until those that remain are under the resource limit this defines.