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Hadoop and map-reduce on multicore machines

I have read a lot about Hadoop and Map-Reduce running on clusters of machines. Does some one know if the Apache distribution can be run on an SMP with several cores. In particular, can multiple Map-Reduce processes be run on the same machine. The scheduler will take care of spreading them across multiple cores. Thanks. - KG

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K Gupta Avatar asked Sep 29 '12 23:09

K Gupta


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1 Answers

Yes. You have multiple map and reduce slots in each machine which are determined by the RAM and CPU (each JVM instance needs 1GB by default so a 8GB machine with 16 cores should still have 7 task slots)

from hadoop wiki

Use the configuration knob: mapred.tasktracker.map.tasks.maximum and mapred.tasktracker.reduce.tasks.maximum to control the number of maps/reduces spawned simultaneously on a TaskTracker. By default, it is set to 2, hence one sees a maximum of 2 maps and 2 reduces at a given instance on a TaskTracker.

You can set those on a per-tasktracker basis to accurately reflect your hardware (i.e. set those to higher nos. on a beefier tasktracker etc.).

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Arnon Rotem-Gal-Oz Avatar answered Nov 15 '22 07:11

Arnon Rotem-Gal-Oz