[jira] [Resolved] (MAPREDUCE-259) Rack-aware Shuffle

["Allen Wittenauer (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/MAPREDUCE-259?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Allen Wittenauer resolved MAPREDUCE-259.
----------------------------------------

    Resolution: Duplicate

> Rack-aware Shuffle
> ------------------
>
>                 Key: MAPREDUCE-259
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-259
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>            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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