Exam AWS Certified Machine Learning - Specialty topic 1 question 90 discussion

Answer is C. https://docs.aws.amazon.com/emr/latest/ManagementGuide/emr-plan-instances-guidelines.html

C is the correct answer. "Long-Running Clusters and Data Warehouses If you are running a persistent Amazon EMR cluster that has a predictable variation in computational capacity, such as a data warehouse, you can handle peak demand at lower cost with Spot Instances. You can launch your master and core instance groups as On-Demand Instances to handle the normal capacity and launch task instance groups as Spot Instances to handle your peak load requirements."

According to :https://docs.aws.amazon.com/emr/latest/ManagementGuide/emr-plan-instances-guidelines.html The task nodes process data but do not hold persistent data in HDFS. If they terminate because the Spot price has risen above your maximum Spot price, no data is lost and the effect on your cluster is minimal. When you launch one or more task instance groups as Spot Instances, Amazon EMR provisions as many task nodes as it can, using your maximum Spot price. This means that if you request a task instance group with six nodes, and only five Spot Instances are available at or below your maximum Spot price, Amazon EMR launches the instance group with five nodes, adding the sixth later if possible.

The correct answer is C

I don't get why the wrong answer are still not updated after more than 1 year of everyone showing docs proving answer C..

Long-running clusters and data warehouses If you are running a persistent Amazon EMR cluster that has a predictable variation in computational capacity, such as a data warehouse, you can handle peak demand at lower cost with Spot Instances. You can launch your primary and core instance groups as On-Demand Instances to handle the normal capacity and launch the task instance group as Spot Instances to handle your peak load requirements.

Only task nodes can be deleted without losing data.

C, If you want to cut cost on an EMR cluster in the most efficient way, use spot instances on the task nodes because it, task nodes do not store data so no risk of data loss

For Long running jobs, you do not want to compromise the Master node(sudden termination) or the core nodes (HDFS data loss). Spot Instances on 20 task nodes are enough cost savings without compromising the job. Hence, C

If your primary concern is the cost, then you can run the master node on spot instances.

Answer: C. https://aws.amazon.com/getting-started/hands-on/optimize-amazon-emr-clusters-with-ec2-spot/ Amazon recommends using On-Demand instances for Master and Core nodes unless you are launching highly ephemeral workloads.

Answer should be C.

Only master node is incorrect. Either use all on spot or only task or core on spot. As per: https://docs.aws.amazon.com/emr/latest/ManagementGuide/emr-plan-instances-guidelines.html Better to use only task node on spot for long running tasks/jobs