Name Node, Secondary Name Node and Job Tracker are known as Master daemons. Task Tracker and Data Nodes are known as slave daemons. Whenever a client submits a Job, the actual processing is going to take place in Task Tracker.
NameNode consists of all Meta data information such as racks, blocks (r1, r2, b1, b2). NN sends its image file to secondary NN every 3sec (Heartbeat Mechanism). Name node is having special feature “Rack Awareness”, it will give information about nodes present in different racks of Hadoop cluster environment.
- Secondary Name Node (Snn) - If NN goes down, Snn will take the image instantaneously and acts like NN and performs the NN functionalities.
- Job Tracker (JT) - it is used for job scheduling and maintenance. It assigns different tasks to Task Tracker and monitors it.
- Task Tracker (TT) - Actual computational processing is going to happen here. It gets in contact with JT and has some heart beat mechanism between them.
For Single Node Hadoop Setup it includes single master node and multiple working nodes. In this case, master consists of Job Tracker, Task Tracker, Name Node (NN) and Data Node (DN). A slave or working nodes act as both the Data Node and Task Tracker. For high level application developments Single Node Hadoop will give limited options (like memory, capacity) only, so it’s not that suitable.
