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From Arun C Murthy <...@hortonworks.com>
Subject Re: MapReduce task-worker assignment
Date Tue, 08 Oct 2013 00:06:39 GMT
Short version: MR provides all the info it can to (about all it's tasks locations) and the
YARN scheduler deals with providing good locality with even assignment.

I don't have a handy link to a doc, but here is an ancient version:

You might find a more recent version of one of my talks if you try really hard… *smile*


On Oct 5, 2013, at 3:12 PM, John Lilley <john.lilley@redpoint.net> wrote:

> Is there a description of how MapReduce under Hadoop 2.0 assigns mapper tasks to preferred
nodes?  I think that someone on the list mentioned previously that it attempted to assign
“one HDFS block per mapper task”, but given that there can be multiple block instances
per data split, how does MapReduce try to obtain an even task assignment while optimizing
data locality?
> Thanks,
> John Lilley
> Chief Architect, RedPoint Global Inc.
> 1515 Walnut Street | Suite 200 | Boulder, CO 80302
> T: +1 303 541 1516  | M: +1 720 938 5761 | F: +1 781-705-2077
> Skype: jlilley.redpoint | john.lilley@redpoint.net | www.redpoint.net

Arun C. Murthy
Hortonworks Inc.

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