mapred.tasktracker.map.tasks.maximum

[Mark Kerzner]

Hi,

I have a cluster with 4 nodes and 32 many cores on each. My default value
for the maximum number of mappers per slot is 1:

  <property>
    <name>mapred.tasktracker.map.tasks.maximum</name>
    <!-- see other kb entry about this one. -->
    <value>1</value>
    <final>true</final>
  </property>
(which I think is wrong).

Howeve, when sizable jobs run, I see 65 mappers working, so it seems that
it does create more than 1 mapper per node.

Questions: what maximum number of mappers would be appropriate in this
situation? Is that the right way to set them?

Thank you. Sincerely,
Mark