I was just explaining to a colleague today how Hadoop 2.0 (aka YARN, which stands for Yet Another Resource Negotiator) differs from Hadoop 1.0. Today's "core Hadoop" consists of HDFS and MapReduce and each have their own master & worker daemon processes. Specifically, NameNode & DataNode for HDFS and JobTracker & TaskTracker for MapReduce. This itself makes sense as HDFS and MapReduce are focused on two different things.
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