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From Fariha Atta <fariha.atta...@gmail.com>
Subject Re: What are uses of taskTracker and JobTracker services?
Date Wed, 30 Jun 2010 05:46:59 GMT

NameNode* serves as a directory namespace manager. It keeps the directory
tree of all files in the file system, and tracks where across the cluster
the file data is kept. It does not store the data of these files itself.

whereas a jobtracker manages job-related parameters.

"The JobTracker is the service within Hadoop that farms out
MapReduce<http://wiki.apache.org/hadoop/MapReduce>tasks to specific
nodes in the cluster, ideally the nodes that have the
data, or at least are in the same rack.

   1. Client applications submit jobs to the Job tracker.

   The JobTracker talks to the
NameNode<http://wiki.apache.org/hadoop/NameNode>to determine the
location of the data

   The JobTracker locates
TaskTracker<http://wiki.apache.org/hadoop/TaskTracker>nodes with
available slots at or near the data

   The JobTracker submits the work to the chosen

[source: http://wiki.apache.org/hadoop/JobTracker]


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