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Posted to mapreduce-issues@hadoop.apache.org by "Mahadev konar (JIRA)" <ji...@apache.org> on 2010/07/07 22:58:53 UTC
[jira] Commented: (MAPREDUCE-1521) Protection against incorrectly
configured reduces
[ https://issues.apache.org/jira/browse/MAPREDUCE-1521?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12886079#action_12886079 ]
Mahadev konar commented on MAPREDUCE-1521:
------------------------------------------
I think Hongs idea seems reasonable.. and also todd is a valid point of disabling this feature by default.
> 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: Mahadev konar
> Priority: Critical
> 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.
> Thoughts?
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