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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-3951) Tasks are not evenly spread throughout cluster in MR2
Date Fri, 22 Feb 2013 20:48:13 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-3951?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13584668#comment-13584668

Todd Lipcon commented on MAPREDUCE-3951:

Seems like so long as the schedulers we expect people to use support this feature, we should
be OK.
> Tasks are not evenly spread throughout cluster in MR2
> -----------------------------------------------------
>                 Key: MAPREDUCE-3951
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-3951
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: scheduler
>    Affects Versions: 0.23.0, 0.24.0
>            Reporter: Todd Lipcon
> In MR1 (at least with the fair and fifo schedulers), if you submit a job that needs fewer
resources than the cluster can provide, the tasks are spread relatively evenly across the
node. For example, submitting a 100-map job to a 50-node cluster, each with 10 slots, results
in 2 tasks on each machine. In MR2, however, the tasks would pile up on the first 10 nodes
of the cluster, leaving the other nodes unused. This is highly suboptimal for many use cases.

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