What method is the MOST cost effective based on these requirements?
Use a mixture of On-Demand and Spot Instances for job execution.
Submit a request for a Spot block to be used for job execution.
Purchase Reserved Instances to be used for job execution.
Submit a request for a one-time Spot Instance for job execution.
Explanations:
Using a mixture of On-Demand and Spot Instances may not guarantee cost savings, as On-Demand Instances are more expensive and there’s no assurance Spot Instances will always be available. Additionally, managing the combination could add complexity.
Spot block instances provide a low-cost, predictable option, and since the job needs to be restarted from the beginning if it fails, the ability to run a specific block duration helps in managing costs effectively.
Reserved Instances are a long-term commitment and not suitable for short-term, unpredictable workloads like nightly jobs that may fail and need to restart. They would be more costly for this use case.
A one-time Spot Instance could be very cost-effective but may not guarantee availability or survival during the job’s runtime, which could be problematic for jobs that need to restart from the beginning.
I judge that the answer is:
Submit a request for a Spot block to be used for job execution.