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From "Arun C Murthy (JIRA)" <j...@apache.org>
Subject [jira] Created: (MAPREDUCE-1521) Protection against incorrectly configured reduces
Date Mon, 22 Feb 2010 17:44:30 GMT
Protection against incorrectly configured reduces

                 Key: MAPREDUCE-1521
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1521
             Project: Hadoop Map/Reduce
          Issue Type: Improvement
          Components: jobtracker
            Reporter: Arun C Murthy
            Assignee: Arun C Murthy
             Fix For: 0.22.0

We've seen a fair number of instances where naive users process huge data-sets (>10TB)
with badly mis-configured #reduces e.g. 1 reduce.

This is a significant problem on large clusters since it takes each attempt of the reduce
a long time to shuffle and then run into problems such as local disk-space etc. Then it takes
4 such attempts.

Proposal: Come up with heuristics/configs to fail such jobs early. 


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