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MapReduce >> mail # user >> Basic Doubt in Hadoop


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Raj Hadoop 2013-04-17, 04:49
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Ramesh R Nair 2013-04-17, 07:36
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Re: Basic Doubt in Hadoop

You are correct, map outputs are stored in LFS not in HDFS.

Regards
Bejoy KS

Sent from remote device, Please excuse typos

-----Original Message-----
From: Ramesh R Nair <[EMAIL PROTECTED]>
Date: Wed, 17 Apr 2013 13:06:32
To: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
Subject: Re: Basic Doubt in Hadoop

Hi Bejoy,

   Regarding the output of Map phase, does  Hadoop store it in local fs or
in HDFS.
   I believe it is in the former. Correct me if I am wrong.

Regards
Ramesh
On Wed, Apr 17, 2013 at 10:30 AM, <[EMAIL PROTECTED]> wrote:

> The data is in HDFS in case of WordCount MR sample.
>
> In hdfs, you have the metadata in NameNode and actual data as blocks
> replicated across DataNodes.
>
> In case of reducer, If a reducer is running on a particular node then you
> have one replica of the blocks in the same node (If there is no space
> issues) and rest replicas on other nodes.
> Regards
> Bejoy KS
>
> Sent from remote device, Please excuse typos
> ------------------------------
> *From: * Raj Hadoop <[EMAIL PROTECTED]>
> *Date: *Tue, 16 Apr 2013 21:49:34 -0700 (PDT)
> *To: *[EMAIL PROTECTED]<[EMAIL PROTECTED]>
> *ReplyTo: * [EMAIL PROTECTED]
> *Subject: *Basic Doubt in Hadoop
>
> Hi,
>
> I am new to Hadoop. I started reading the standard Wordcount program. I
> got this basic doubt in Hadoop.
>
> After the Map - Reduce is done, where is the output generated?  Does the
> reducer ouput sit on individual DataNodes ? Please advise.
>
>
> Thanks,
> Raj
>