Which solution will meet these requirements MOST cost-effectively?
Split the 12 instances across two Availability Zones in the chosen AWS Region. Run two instances in each Availability Zone as On-Demand Instances with Capacity Reservations. Run four instances in each Availability Zone as Spot Instances.
Split the 12 instances across three Availability Zones in the chosen AWS Region. In one of the Availability Zones, run all four instances as On-Demand Instances with Capacity Reservations. Run the remaining instances as Spot Instances.
Split the 12 instances across three Availability Zones in the chosen AWS Region. Run two instances in each Availability Zone as On-Demand Instances with a Savings Plan. Run two instances in each Availability Zone as Spot Instances.
Split the 12 instances across three Availability Zones in the chosen AWS Region. Run three instances in each Availability Zone as On-Demand Instances with Capacity Reservations. Run one instance in each Availability Zone as a Spot Instance.
Explanations:
Using Capacity Reservations for On-Demand Instances adds cost without benefiting the SLAs. The combination of Spot Instances with On-Demand Instances may not guarantee the required high availability, especially during failures when capacity needs to be preserved.
Running four instances in one Availability Zone as On-Demand Instances with Capacity Reservations increases cost unnecessarily. Additionally, relying on Spot Instances may not guarantee the necessary capacity during failures, which would violate the SLAs.
While using Savings Plans for On-Demand Instances offers a cost reduction, it does not provide sufficient reliability during system failures. Spot Instances, by nature, can be interrupted, making them unsuitable for high availability requirements.
Running On-Demand Instances with Capacity Reservations ensures high availability and meets SLAs for scheduled jobs. Spot Instances provide a cost-effective solution for the remaining capacity, without jeopardizing the reliability for critical workloads.