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From "Arun C Murthy (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-1721) Rack-aware Shuffle
Date Fri, 12 Oct 2007 12:03:52 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-1721?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Arun C Murthy updated HADOOP-1721:
----------------------------------

        Fix Version/s:     (was: 0.15.0)
    Affects Version/s:     (was: 0.14.2)
               Status: Open  (was: Patch Available)

> Rack-aware Shuffle
> ------------------
>
>                 Key: HADOOP-1721
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1721
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: mapred
>            Reporter: Arun C Murthy
>            Assignee: Arun C Murthy
>
> We could try and experiment with *rack-aware* scheduling of fetches per-reducer. Given
the disparities between in-rack and off-rack bandwidth it could be a improvement to do something
along these lines:
> {noformat}
> if (no. of known map-output locations > than no. of copier threads) {
>   try to schedule 75% of copies off-rack
>   try schedule 25% of copies in-rack
> }
> {noformat}
> This could lead to better utilization of both in-rack & switch b/w...
> Clearly we want to schedule more cross-switch than in-rack since off-rack copies will
take significantly more time; hence the 75-25 split.

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