You set mapred.tasktracker.reduce.tasks.maximum to a value of 4 on a cluster running mapreduce v1 (MRv1). How many reducers will run for any given job?

Question

Options

• AMaximum of 4 reducers, but the actual number of reducers that run for any given job is based on the
• Ba maximum of 4 reducer's, but the actual number of reducer's that run for any given job is based on
• CFour reducer's will run. Once set by the cluster administrator, this parameter can't be overridden
• DThe number of reducer's for any given job is set by the developer

• A
  13% (6)
• B
  81% (39)
• C
  2% (1)
• D
  4% (2)

Explanation

mapred.tasktracker.reduce.tasks.maximum The maximum number of reduce tasks that will be run simultaneously by a task tracker. A reducer uses intermediate data as input. * The mapper output (intermediate data) is stored on the Local file system (NOT HDFS) of each individual mapper nodes. * Reducers start copying intermediate key-value pairs from the mappers as soon as they are available. The progress calculation also takes in account the processing of data transfer which is done by reduce process, therefore the reduce progress starts showing up as soon as any intermediate key-value pair for a mapper is available to be transferred to reducer.

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