If a MapReduce job has mapreduce.reduce.memory.mb=2048 and mapreduce.reduce.java.opts=-Xmx1536m, what is the maximum heap size allocated to each reduce task JVM?

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Hadoop - Performance Tuning

If a MapReduce job has mapreduce.reduce.memory.mb=2048 and mapreduce.reduce.java.opts=-Xmx1536m, what is the maximum heap size allocated to each reduce task JVM?

A2048 MB

B512 MB

C1536 MB

D3584 MB

Step-by-Step Solution

Solution:

Step 1: Understand memory and JVM heap settings
mapreduce.reduce.memory.mb sets total memory for reduce task container; java.opts sets JVM heap size.
Step 2: Identify JVM heap size from java.opts
-Xmx1536m means max JVM heap is 1536 MB.
Final Answer:
1536 MB -> Option C
Quick Check:
JVM heap = value in mapreduce.reduce.java.opts [OK]

Quick Trick: JVM heap max is from -Xmx in java.opts, not total container memory [OK]

Common Mistakes:

Assuming total container memory equals JVM heap
Adding memory values incorrectly
Ignoring java.opts setting

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If a MapReduce job has mapreduce.reduce.memory.mb=2048 and mapreduce.reduce.java.opts=-Xmx1536m, what is the maximum heap size allocated to each reduce task JVM?

Step 1: Understand memory and JVM heap settings

Step 2: Identify JVM heap size from java.opts

Final Answer:

Quick Check:

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