Reserve compute capacity with On-Demand Capacity Reservations
On-Demand Capacity Reservations allow you to reserve compute capacity for your Amazon EC2 instances in a specific Availability Zone for any duration. If you have strict capacity requirements, and are running business-critical workloads that require a certain level of long or short-term capacity assurance, we recommend that you create a Capacity Reservation to ensure that you always have access to Amazon EC2 capacity when you need it, for as long as you need it.
You can create Capacity Reservations at any time, without entering into a one-year or three-year term commitment. The capacity becomes available and billing starts as soon as the Capacity Reservation is provisioned in your account. When you no longer need the capacity assurance, cancel the Capacity Reservation to release the capacity and to stop incurring charges. You can also use the billing discounts offered by Savings Plans and Regional Reserved Instances to reduce the cost of a Capacity Reservation.
When you create a Capacity Reservation, you specify:
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The Availability Zone in which to reserve the capacity
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The number of instances for which to reserve capacity
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The instance attributes, including the instance type, platform, Availability Zone, and tenancy
Capacity Reservations can only be used by instances that match their attributes. By default, Capacity Reservations automatically match new instances and running instances that have matching attributes (instance type, platform, Availability Zone, and tenancy). This means that any instance with matching attributes automatically runs in the Capacity Reservation. However, you can also target a Capacity Reservation for specific workloads. This allows you to explicitly control which instances are allowed to run in that reserved capacity.
You can specify how the reservation ends. You can choose to cancel the Capacity Reservation or end it automatically at a specified time. If you specify an end time, the Capacity Reservation is canceled within an hour of the specified time. For example, if you specify 5/31/2019, 13:30:55, the Capacity Reservation is guaranteed to end between 13:30:55 and 14:30:55 on 5/31/2019.
After a reservation ends, you can no longer target instances to the Capacity Reservation. Instances running in the reserved capacity continue to run uninterrupted. If instances targeting a Capacity Reservation are stopped, you cannot restart them until you remove their Capacity Reservation targeting preference or configure them to target a different Capacity Reservation. For more information, see Modify the Capacity Reservation settings of your instance.
Contents
- Differences between Capacity Reservations, Reserved Instances, and Savings Plans
- Supported platforms
- Quotas
- Limitations
- Capacity Reservation pricing and billing
- Create a Capacity Reservation
- View the state of a Capacity Reservation
- Launch instances into an existing Capacity Reservation
- Modify an active Capacity Reservation
- Modify the Capacity Reservation settings of your instance
- Move capacity between Capacity Reservations
- Split off available capacity from an existing Capacity Reservation
- Cancel a Capacity Reservation
- Capacity Reservation groups
- Create Capacity Reservations in cluster placement groups
- Capacity Reservations in Local Zones
- Capacity Reservations in Wavelength Zones
- Capacity Reservations on AWS Outposts
- Shared Capacity Reservations
- Capacity Reservation Fleets
- Monitor Capacity Reservations usage with CloudWatch metrics
- Monitor Capacity Reservations utilization using EventBridge
- Capacity Reservation utilization notifications from AWS Health
Differences between Capacity Reservations, Reserved Instances, and Savings Plans
The following table highlights key differences between Capacity Reservations, Reserved Instances, and Savings Plans:
Capacity Reservations | Zonal Reserved Instances | Regional Reserved Instances | Savings Plans | |
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Term | No commitment required. Can be created and canceled as needed. | Requires a fixed one-year or three-year commitment | ||
Capacity benefit | Capacity reserved in a specific Availability Zone. | No capacity reserved. | ||
Billing discount | No billing discount. † | Provides a billing discount. | ||
Instance Limits | Your On-Demand Instance limits per Region apply. | Default is 20 per Availability Zone. You can request a limit increase. | Default is 20 per Region. You can request a limit increase. | No limit. |
† You can combine Capacity Reservations with Savings Plans or Regional Reserved Instances to receive a discount.
For more information, see the following:
Supported platforms
You must create the Capacity Reservation with the correct platform to ensure that it properly matches with your instances. Capacity Reservations support the following platforms:
Linux/UNIX
Linux with SQL Server Standard
Linux with SQL Server Web
Linux with SQL Server Enterprise
SUSE Linux
Red Hat Enterprise Linux
RHEL with SQL Server Standard
RHEL with SQL Server Enterprise
RHEL with SQL Server Web
RHEL with HA
RHEL with HA and SQL Server Standard
RHEL with HA and SQL Server Enterprise
Ubuntu Pro
Windows
Windows with SQL Server
Windows with SQL Server Web
Windows with SQL Server Standard
Windows with SQL Server Enterprise
When you purchase a Capacity Reservation, you must specify the platform that represents the operating system for your instance.
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For SUSE Linux and RHEL distributions, excluding BYOL, you must choose the specific platform. For example, the SUSE Linux or Red Hat Enterprise Linux platform.
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For all other Linux distributions (including Ubuntu), choose the Linux/UNIX platform.
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If you bring your existing RHEL subscription (BYOL), you must choose the Linux/UNIX platform.
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For Windows with SQL Standard, Windows with SQL Server Enterprise, and Windows with SQL Server Web, you must choose the specific platform.
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For all other Windows versions, excluding BYOL which is not supported, choose the Windows platform.
Quotas
The number of instances for which you are allowed to reserve capacity is based on your account's On-Demand Instance quota. You can reserve capacity for as many instances as that quota allows, minus the number of instances that are already running.
Quotas apply to running instances only. If your instance is pending, stopping, stopped, or hibernated, it does not count towards your quota.
Limitations
Before you create Capacity Reservations, take note of the following limitations and restrictions.
Active and unused Capacity Reservations count toward your On-Demand Instance limits.
Capacity Reservations are not transferable from one AWS account to another. However, you can share Capacity Reservations with other AWS accounts. For more information, see Shared Capacity Reservations.
Zonal Reserved Instance billing discounts do not apply to Capacity Reservations.
Capacity Reservations can be created in cluster placement groups. Spread and partition placement groups are not supported.
Capacity Reservations can't be used with Dedicated Hosts. Capacity Reservations can be used with Dedicated Instances.
[Windows instances] Capacity Reservations can't be used with Bring Your Own License (BYOL).
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Capacity Reservations do not ensure that a hibernated instance can resume after you try to start it.