How can I modify my Reserved Instance after I resize my instance?

Short description

Some instance platforms, such as SUSE and RHEL, don't allow for instance flexibility. Instance flexibility applies discounts to instance usage for instances in the same family, generation, and attribute regardless of the instance size. For instance platforms that don't allow for instance flexibility, you can modify the Reserved Instance's Availability Zone, instance size, and scope to meet changing needs. Note that instance changes must stay within the same family and generation. You can divide or merge existing Reserved Instances into different instance sizes across the same family if the footprint of your reservation remains the same.

Maintaining the same footprint retains the discount that your previously purchased Reserved Instance provides.

Resolution

Modify your Reserved Instance

Example scenario 1

You have a 5.16xlarge SUSE Linux-based EC2 instance. You purchased a matching Regional, convertible r5.16xlarge Reserved Instance for this instance. Your application's needs changed, and you now require an r5.24xlarge instance. Instance flexibility doesn't apply to SUSE Linux-based instances. You don't want to lose the discount that the r5.16xlarge Reserved Instance provides.

In this scenario, purchase an additional r5.8xlarge Reserved Instance, and merge it with your existing r5.16xlarge Reserved Instance. This provides coverage for your running r5.24xlarge instance.

An r5.24xlarge instance has a footprint of 192 units. This means you need a Reserved Instance with a matching footprint (192 units) to cover the new r5.24xlarge instance. An r5.16xlarge instance has a footprint of 128 units. The r5.8xlarge Reserved Instance has a footprint of 64 units. Merging these instances allows the new reservation (128 units + 64 units = 192 units) to cover the r5.24xlarge running instance.

Example scenario 2

You have a Regional, Convertible Reserved Instance to cover a t2.large (4 units) RHEL-based running instance. Your requirements changed. To run your application, you now need four t2.small (1 unit each) EC2 instances behind a load balancer.

In this scenario, divide the t2.large reservation into four t2.small reservations to cover your newly launched instances.

For more information, see Modify Reserved Instances.

Use a Savings Plan

As an alternative to modifying your instance, you can use a Savings Plan.

With Savings Plans, you receive a discount for committing to a set amount of usage over a 1-year or 3-year term. Usage is measured in dollars per hour. The following are Savings Plan options:

• Compute Saving Plans: Offer the most flexibility by automatically applying to EC2 instance usage regardless of instance family, size, Availability Zone, AWS Region, OS, or tenancy.
• EC2 Instance Savings Plans: Offer savings in exchange for a commitment to use individual instance families in a specific Region. This option automatically applies on running instances of the selected instance family in that Region regardless of Availability Zone, size, OS, or tenancy.

Related information

How Reserved Instances are applied

Differences between Standard and Convertible Reserved Instances