AWS Certified Sysops Administrator Associate · Free Practice Question Medium
Question 9
A university is using a distributed computing application to run complex calculations on a fleet of Amazon EC2 instances. The calculations will be running for at least 1 year. The application uses 2 control nodes and between 8 and 24 worker nodes as required. The control nodes run continuously while the worker nodes run for 8 hours a day and are launched when required.
What is the MOST cost-effective pricing model for the application? (Select TWO.)
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A
Use Dedicated Hosts for the control nodes.
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B
Use Reserved Instances for the worker nodes.
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C
Use Spot Instances for the control nodes and On-Demand Instances if there is no Spot availability.
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D
Use Reserved Instances for the control nodes.
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E
Use Spot Instances for the worker nodes and On-Demand Instances if there is no Spot availability.
Reveal correct answers
Correct answers: D, E
Explanation
The worker nodes run continuously and will run for at least 1 year so using reserved instances would be the most cost-effective choice as these instances cannot risk being terminated. For the worker nodes, a mixture of Spot and on-demand would make the most sense. Spot can be used when there is capacity which will provide a significant cost saving. When there is no Spot capacity available on-demand instances can be used.
CORRECT: "Use Reserved Instances for the control nodes" is the correct answer.
CORRECT: "Use Spot Instances for the worker nodes and On-Demand Instances if there is no Spot availability" is also a correct answer.
INCORRECT: "Use Dedicated Hosts for the control nodes" is incorrect. This would not be cost-effective and is not required for this scenario.
INCORRECT: "Use Reserved Instances for the worker nodes" is incorrect. As the worker nodes are variable in number and only run for 8 hours a day, this would not make sense.
INCORRECT: "Use Spot Instances for the control nodes and On-Demand Instances if there is no Spot availability" is incorrect. The control nodes run continuously for the whole year so Spot instances would not be suitable as the instances could be terminated from time to time.
References:
https://aws.amazon.com/ec2/pricing/
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Discussion
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