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From Owen O'Malley <omal...@apache.org>
Subject Re: only one reducer running in a hadoop cluster
Date Mon, 09 Feb 2009 08:20:25 GMT

On Feb 7, 2009, at 11:52 PM, Nick Cen wrote:

> Hi,
>
> I hava a hadoop cluster with 4 pc. And I wanna to integrate hadoop and
> lucene together, so i copy some of the source code from nutch's  
> Indexer
> class, but when i run my job, i found that there is only 1 reducer  
> running
> on 1 pc, so the performance is not as far as expect.

Set mapred.reduce.tasks in your configuration to the number of  
reduces, you want your jobs to have by default. Typically this should  
be 0.99 * mapred.tasktracker.reduce.tasks.maximum * number of computers.

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