MAPREDUCE Framework consists of a single JOB Tracker PER Cluster, one Task Tracker per NODE. Usually A cluster has multiple nodes, so each cluster has single Job Tracker and multiple TaskTrackers.JobTracker can schedule the job and monitor the Task Trackers. If Task Tracker FAILED to execute tasks, try to re-execute the failed tasks.

TaskTracker follow the JobTracker’s instructions and execute the tasks. As a slave node, it report the job status to Master JobTracker in the form of Heartbeat. 

MapReduce Framework consists of a single Job Tracker per Cluster, one Task Tracker per node. Usually A cluster has multiple nodes, so each cluster has single Job Tracker and multiple TaskTrackers.JobTracker can schedule the job and monitor the Task Trackers. If Task Tracker failed to execute tasks, try to re-execute the failed tasks.

TaskTracker follow the JobTracker’s instructions and execute the tasks. As a slave node, it report the job status to Master JobTracker in the form of Heartbeat.