Hadoop is comprised of five separate daemons. Each of these daemons runs in its own JVM.
Following 3 Daemons run on Master nodes.NameNode - This daemon stores and maintains the metadata for HDFS.
Secondary NameNode - Performs housekeeping functions for the NameNode. JobTracker - Manages MapReduce jobs, distributes individual tasks to machines running the Task Tracker. Following 2 Daemons run on each Slave nodes DataNode – Stores actual HDFS data blocks.
TaskTracker – It is Responsible for instantiating and monitoring individual Map and Reduce tasks.