Use Capacity Reservations to reserve On-Demand capacity in EC2 Fleet - Amazon Elastic Compute Cloud
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Use Capacity Reservations to reserve On-Demand capacity in EC2 Fleet

You can configure a fleet to use On-Demand Capacity Reservations first when launching On-Demand Instances by setting the usage strategy for Capacity Reservations to use-capacity-reservations-first. You can use this setting in conjunction with the allocation strategy for On-Demand Instances (lowest-price or prioritized).

When unused Capacity Reservations are used to fulfil On-Demand capacity:

  • The fleet uses unused Capacity Reservations to fulfill On-Demand capacity up to the target On-Demand capacity.

  • If multiple instance pools have unused Capacity Reservations, the On-Demand allocation strategy (lowest-price or prioritized) is applied.

  • If the number of unused Capacity Reservations is less than the On-Demand target capacity, the remaining On-Demand target capacity is launched according to the On-Demand allocation strategy (lowest-price or prioritized).

You can only use unused On-Demand Capacity Reservations for fleets of type instant.

For examples of how to configure a fleet to use Capacity Reservations to fulfil On-Demand capacity, see Example CLI configurations for EC2 Fleet. For more information, see Reserve compute capacity with EC2 On-Demand Capacity Reservations and the On-Demand Capacity Reservation FAQs.