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From Roy Smith <...@panix.com>
Subject How does hadoop decide how many reducers to run?
Date Fri, 11 Jan 2013 22:59:29 GMT
I ran a big job the other day on a cluster of 4 m2.4xlarge EC2 instances.  Each instance is
8 cores, so 32 cores total.  Hadoop ran 16 reducers, followed by a second wave of 12.  It
seems to me it was only using half the available cores.  Is this normal?  Is there some way
to force it to use all the cores?

Roy Smith

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