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From "Toby DiPasquale" <codeslin...@gmail.com>
Subject Hadoop ignores attempts to set mappers/machine?
Date Mon, 17 Sep 2007 12:01:42 GMT
Hi all,

No matter what I try, the number of mapper tasks on a given machine is
always 2. JobConf.setNumMapTasks(X) has no effect, nor does setting
mapred.map.tasks in the mapred-default.xml configuration. Why are
these settings ignored? How can I truly increase the number of map
tasks on a given machine?

I ran a job last night (using 0.14.1) that took 31.5 minutes to map
7.5 GB (on HDFS, not s3fs) and then 78 seconds to reduce the results
of that map (starting from 15% complete when the map phase hit 100%).
The map took so long because only 6 - 8 out of the 171 mappers were
running at any one time. I'd really like to know how to move the
needle on this one so if anyone has any insight, I'd really appreciate
it. Thanks.

Toby DiPasquale

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