Which MapReduce daemon runs on each slave node and participates in job execution?
Single instance of a Task Tracker is run on each Slave node. Task tracker is run as
a separate JVM process.
Reference:24 Interview Questions & Answers for Hadoop MapReduce developers,What is
configuration of a typical slave node on Hadoop cluster? How many JVMs run on a slave node?
http://www.fromdev.com/2010/12/interview-questions-hadoop-mapreduce.html(See answer to
question no. 5)