Split off available capacity from an existing Capacity Reservation
If you have available capacity in an existing Capacity Reservation that you want to assign to a specific workload or use to carry out a specific action, you can split off the available capacity into a new Capacity Reservation. For example, to partially share a Capacity Reservation with another account, you can split off some of the available capacity to create a smaller sized Capacity Reservation. The smaller sized Capacity Reservation can then be shared with the other account using AWS Resource Access Manager (AWS RAM).
When you split available capacity from an existing Capacity Reservation, a new Capacity Reservation is automatically created. The existing Capacity Reservation will be unchanged, except for the reduced total capacity from the number of instances split off. Instances that are running in the existing Capacity Reservation are not affected. You can split the existing Capacity Reservation into only one new Capacity Reservation. In order to split off the available capacity, the existing Capacity Reservation must be active and owned by your AWS account.
The new Capacity Reservation will have the same configuration as the existing Capacity Reservation except for tags. By default, the new Capacity Reservation doesn't have any tags. You can specify new tags during the split operation. The new Capacity Reservation can also be modified after it is created, if necessary.
The maximum quantity of instances to split from an existing Capacity Reservation is the size of the reservation minus one. For example, if a Capacity Reservation has a reserved capacity of 10 slots, you can split off a maximum of nine slots if all nine slots are available.
Considerations
-
Resource groups – If the existing Capacity Reservation belongs to a resource group, the new Capacity Reservation will not be automatically added to the resource group. You can add the new Capacity Reservation to a resource group after it is created, if necessary.
-
Sharing – If the existing Capacity Reservation is shared with a consumer account, the new Capacity Reservation will not be automatically shared with the consumer account. You can share the new Capacity Reservation after it is created, if necessary.
-
Cluster placement group – If the existing Capacity Reservation is part of a cluster placement group, the new Capacity Reservation will be created in the same cluster placement group.
Note
Splitting capacity from a Capacity Block isn't supported.
Control access for splitting Capacity Reservations using tags
You can use tags to control access to Amazon EC2 resources, including splitting available capacity from an existing Capacity Reservation to create a new Capacity Reservation. For more information, see Controlling access to AWS resources using tags in the IAM User Guide.
To control access for splitting a Capacity Reservation using tags, make sure that you specify both resource and request tags in the policy statement because IAM policies are evaluated against both the source Capacity Reservation and the newly created Capacity Reservation.
The following example policy includes the ec2:ResourceTag
condition key with the tag Owner=ExampleDepartment1
for the source Capacity Reservation and the ec2:RequestTag
condition key with the tag stack=production
for the newly created Capacity Reservation.
{ "Statement": [ { "Sid": "AllowSourceCapacityReservation", "Effect": "Allow", "Action": "ec2:CreateCapacityReservationBySplitting", "Resource": "arn:aws:ec2:region:account:capacity-reservation/cr-1234567890abcdef0", "Condition": { "StringEquals": { "ec2:ResourceTag/Owner": "ExampleDepartment1" } } }, { "Sid": "AllowNewlyCreatedCapacityReservation", "Effect": "Allow", "Action": ["ec2:CreateCapacityReservationBySplitting", "ec2:CreateTags"], "Resource": "arn:aws:ec2:region:account:capacity-reservation/*", "Condition": { "StringEquals": { "ec2:RequestTag/stack": "production" } } } ] }
Split off available capacity using the Amazon EC2 console or the AWS CLI
To split off available capacity from an existing Capacity Reservation and create a new Capacity Reservation, you can use the Amazon EC2 console or the AWS CLI.