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List:       hadoop-dev
Subject:    Re: Question regarding network data transfer
From:       Harsh J <harsh () cloudera ! com>
Date:       2011-05-29 2:49:15
Message-ID: BANLkTi=BJrG0UTqcGGE2vXwbRpFHcoyN9g () mail ! gmail ! com
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Aishwarya,

On Sun, May 29, 2011 at 6:49 AM, Aishwarya Venkataraman
<avenkata@cs.ucsd.edu> wrote:
> So how does reducer obtain the mapper's output ? Does it make a network call
> and read data from mappers local storage or does the mapper send the data ?

The mappers store the files at a location that is accessibly by the
TaskTracker's HTTP servlet. The reducer fetches all successful map
attempt outputs from the TaskTrackers when they initialize.

-- 
Harsh J
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