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From "Dror, Ittay" <id...@akamai.com>
Subject Why is Hadoop always running just 4 tasks?
Date Wed, 11 Dec 2013 15:59:46 GMT
I have a cluster of 4 machines with 24 cores and 7 disks each.

On each node I copied from local a file of 500G. So I have 4 files in hdfs with many blocks.
My replication factor is 1.

I run a job (a scalding flow) and while there are 96 reducers pending, there are only 4 active
map tasks.

What am I doing wrong? Below is the configuration

Thanks,
Ittay

<configuration>
<property>
<name>mapred.job.tracker</name>
  <value>master:54311</value>
</property>

<property>
 <name>mapred.map.tasks</name>
 <value>96</value>
</property>

<property>
  <name>mapred.reduce.tasks</name>
  <value>96</value>
</property>

<property>
<name>mapred.local.dir</name>
<value>/hdfs/0/mapred/local,/hdfs/1/mapred/local,/hdfs/2/mapred/local,/hdfs/3/mapred/local,/hdfs/4/mapred/local,/hdfs/5/mapred/local,/hdfs/6/mapred/local,/hdfs/7/mapred/local</value>
</property>

<property>
<name>mapred.tasktracker.map.tasks.maximum</name>
<value>24</value>
</property>

<property>
    <name>mapred.tasktracker.reduce.tasks.maximum</name>
    <value>24</value>
</property>
</configuration>

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