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From "Vinod K V (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-989) Allow segregation of DistributedCache for maps and reduces
Date Thu, 17 Sep 2009 06:23:59 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-989?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12756380#action_12756380
] 

Vinod K V commented on MAPREDUCE-989:
-------------------------------------

Talked with Milind offline who explained me the use case. So, the segregation is actually
intended for optimizing run-times of tasks by not downloading cache files that are not needed
by them.

For e.g., setup tasks don't need dist-cache files at all and so will run faster if they don't
download files intended for maps/reduces. Also for jobs which need dist-cache files only for
reduces, the maps, which may be much larger in number than reduces, will run faster and the
overall job-execution time will improve.

> Allow segregation of DistributedCache for maps and reduces
> ----------------------------------------------------------
>
>                 Key: MAPREDUCE-989
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-989
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: client
>            Reporter: Arun C Murthy
>
> Applications might have differing needs for files in the DistributedCache wrt maps and
reduces. We should allow them to specify them separately.

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