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Subject: Problems increasing number of tasks per node
From: Joel Welling <welling@psc.edu>
Reply-To: welling@psc.edu
To: core-user@hadoop.apache.org
Cc: welling@psc.edu
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Organization: Pittsburgh Supercomputing Center
Date: Tue, 23 Sep 2008 14:41:13 -0400
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Hi folks;
  I have a small cluster, but each node is big- 8 cores each, with lots
of IO bandwidth.  I'd like to increase the number of simultaneous map
and reduce tasks scheduled per node from the default of 2 to something
like 8.
  My understanding is that I should be able to do this by increasing
mapred.tasktracker.reduce.tasks.maximum and
mapred.tasktracker.map.tasks.maximum , but doing so does not increase
the number of tasks.  I've been running gridmix with these parameters
set to 4, but the average number of tasks per node stays at 4, with 2
reduce and 2 map.  
  Am I missing something?  Do I need to adjust something else as well?

Thanks,
-Joel
 welling@psc.edu