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From praveenesh kumar <praveen...@gmail.com>
Subject Reduce > copy at 0.00 MB/s
Date Wed, 25 Jan 2012 10:04:14 GMT
Hey,

Can anyone explain me what is reduce > copy phase in the reducer section ?
The (K,List(V)), is passed to the reducer. Is reduce > copy representing
copying of K,List(V) on the reducer from all mappers ?

I am monitoring my jobs on the cluster, using Jobtracker url.
I am seeing for most of  my reducing jobs, something like this :

task_201201250352_0001_r_000000    31.05% reduce > copy (395 of 424 at 0.00
MB/s) > 25-Jan-2012 03:54:06

task_201201250352_0001_r_000001    30.73% reduce > copy (391 of 424 at 0.00
MB/s) > 25-Jan-2012 03:54:06

task_201201250352_0001_r_000002    30.89% reduce > copy (393 of 424 at 0.00
MB/s) > 25-Jan-2012 03:54:06


............................

Can anyone explain me why the speed is 0.00 MB/s. Job is running fine.
Is it because this reduce > copy is happening on the same machine.

Thanks,
Praveenesh

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