Differences between primary, core and task nodes in Amazon EMR cluster

The key differences between primary, core, and task nodes in an Amazon EMR cluster are:

Primary Node (also known as Master Node):

• The primary node is responsible for coordinating the cluster and managing the execution of jobs.
• It runs the main Hadoop services, such as the JobTracker, NameNode, and ResourceManager.
• There is only one primary node in an EMR cluster.
• The primary node cannot be terminated during the lifetime of the cluster, as it is essential for the cluster's operation.

Core Nodes:

• Core nodes host the Hadoop Distributed File System (HDFS) and run the DataNode and TaskTracker services.
• They are responsible for storing and processing data in the cluster.
• Core nodes cannot be removed from the cluster without risking data loss, as they contain the persistent data in HDFS.
• You should reserve core nodes for the capacity that is required until your cluster completes.

Task Nodes:

• Task nodes are used for running tasks and do not host HDFS. They can be added or removed from the cluster as needed, without the risk of data loss.
• Task nodes are ideal for handling temporary or burst workloads, as you can launch task instance fleets on Spot Instances to increase capacity while minimizing costs.
• The cluster will never scale below the minimum constraints set in the managed scaling policy.

Here's a table summarizing the key differences:

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More details regarding,

1. Selecting and deploying an Amazon EMR cluster: click here
2. Estimating Amazon EMR cluster capacity: click here