Amazon EC2 | Reserved Instances

Question 1

When should I use the Classic Load Balancer and when should I use the Application Load Balancer?

Reserved Instances

Amazon EC2 | Compute

Answer 1

The Classic Load Balancer is ideal for simple load balancing of traffic across multiple EC2 instances, while the Application Load Balancer is ideal for applications needing advanced routing capabilities, microservices, and container-based architectures. Please visit Elastic Load Balancing for more information.

Question 2

What is a Reserved Instance?

Reserved Instances

Amazon EC2 | Compute

Answer 2

A Reserved Instance (RI) is an EC2 offering that provides you with a significant discount on EC2 usage when you commit to a one-year or three-year term.

Question 3

What are the differences between Standard RIs and Convertible RIs?

Reserved Instances

Amazon EC2 | Compute

Answer 3

Standard RIs offer a significant discount on EC2 instance usage when you commit to a particular instance family. Convertible RIs offer you the option to change your instance configuration during the term, and still receive a discount on your EC2 usage. For more information on Convertible RIs, please click here.

Question 4

Do RIs provide a capacity reservation?

Reserved Instances

Amazon EC2 | Compute

Answer 4

Yes, when a Standard or Convertible RI is scoped to a specific Availability Zone (AZ), instance capacity matching the exact RI configuration is reserved for your use (these are referred to as “zonal RIs”). Zonal RIs give you additional confidence in your ability to launch instances when you need them.

You can also choose to forego the capacity reservation and purchase Standard or Convertible RIs that are scoped to a region (referred to as “regional RIs”). Regional RIs automatically apply the discount to usage across Availability Zones and instance sizes in a region, making it easier for you to take advantage of the RI’s discounted rate.

Question 5

When should I purchase a zonal RI?

Reserved Instances

Amazon EC2 | Compute

Answer 5

If you want to take advantage of the capacity reservation, then you should buy an RI in a specific Availability Zone.

Question 6

When should I purchase a regional RI?

Reserved Instances

Amazon EC2 | Compute

Answer 6

If you do not require the capacity reservation, then you should buy a regional RI. Regional RIs provide AZ and instance size flexibility, which offers broader applicability of the RI’s discounted rate.

Question 7

What are Availability Zone and instance size flexibility?

Reserved Instances

Amazon EC2 | Compute

Answer 7

Availability Zone and instance size flexibility make it easier for you to take advantage of your regional RI’s discounted rate. Availability Zone flexibility applies your RI’s discounted rate to usage in any Availability Zone in a region, while instance size flexibility applies your RI’s discounted rate to usage of any size within an instance family. Let’s say you own an m5.2xlarge Linux/Unix regional RI with default tenancy in US East (N.Virginia). Then this RI’s discounted rate can automatically apply to two m5.xlarge instances in us-east-1a or four m5.large instances in us-east-1b.

Question 8

What types of RIs provide instance size flexibility?

Reserved Instances

Amazon EC2 | Compute

Answer 8

Linux/Unix regional RIs with the default tenancy provide instance size flexibility. Instance size flexibility is not available on RIs of other platforms such as Windows, Windows with SQL Standard, Windows with SQL Server Enterprise, Windows with SQL Server Web, RHEL, and SLES.

Question 9

Do I need to take any action to take advantage of Availability Zone and instance size flexibility?

Reserved Instances

Amazon EC2 | Compute

Answer 9

Regional RIs do not require any action to take advantage of Availability Zone and instance size flexibility.

Question 10

I own zonal RIs how do I assign them to a region?

Reserved Instances

Amazon EC2 | Compute

Answer 10

You can assign your Standard zonal RIs to a region by modifying the scope of the RI from a specific Availability Zone to a region from the EC2 management console or by using the ModifyReservedInstances API.

Question 11

How do I purchase an RI?

Reserved Instances

Amazon EC2 | Compute

Answer 11

To get started, you can purchase an RI from the EC2 Management Console or by using the AWS CLI. Simply specify the instance type, platform, tenancy, term, payment option, and region or Availability Zone.

Question 12

Can I purchase an RI for a running instance?

Reserved Instances

Amazon EC2 | Compute

Answer 12

Yes, AWS will automatically apply an RI’s discounted rate to any applicable instance usage from the time of purchase. Visit the Getting Started page to learn more.

Question 13

Can I control which instances are billed at the discounted rate?

Reserved Instances

Amazon EC2 | Compute

Answer 13

No. AWS automatically optimizes which instances are charged at the discounted rate to ensure you always pay the lowest amount. For information about billing, and how it applies to RIs, see Billing Benefits and Payment Options.

Question 14

How does instance size flexibility work?

Reserved Instances

Amazon EC2 | Compute

Answer 14

EC2 uses the scale shown below, to compare different sizes within an instance family. In the case of instance size flexibility on RIs, this scale is used to apply the discounted rate of RIs to the normalized usage of the instance family. For example, if you have an m5.2xlarge RI that is scoped to a region, then your discounted rate could apply towards the usage of 1 m5.2xlarge or 2 m5.xlarge instances.

Click here to learn more about how instance size flexibility of RIs applies to your EC2 usage. And click here to learn about how instance size flexibility of RIs is presented in the Cost and Usage Report.

Instance Size

Normalization Factor

nano

0.25

micro 0.5

small 1

medium 2

large 4

xlarge 8

2xlarge 16

4xlarge 32

8xlarge 64

9xlarge 72

10xlarge 80

12xlarge 96

16xlarge 128

18xlarge 144

24xlarge 192

32xlarge 256

Question 15

Can I change my RI during its term?

Reserved Instances

Amazon EC2 | Compute

Answer 15

Yes, you can modify the Availability Zone of the RI, change the scope of the RI from Availability Zone to region (and vice-versa), change the network platform from EC2-VPC to EC2-Classic (and vice versa) or modify instance sizes within the same instance family (on the Linux/Unix platform).

Question 16

Can I change the instance type of my RI during its term?

Reserved Instances

Amazon EC2 | Compute

Answer 16

Yes, Convertible RIs offer you the option to change the instance type, operating system, tenancy or payment option of your RI during its term. Please refer to the Convertible RI section of the FAQ for additional information.

Question 17

What are the different payment options for RIs?

Reserved Instances

Amazon EC2 | Compute

Answer 17

You can choose from three payment options when you purchase an RI. With the All Upfront option, you pay for the entire RI term with one upfront payment. With the Partial Upfront option, you make a low upfront payment and are then charged a discounted hourly rate for the instance for the duration of the RI term. The No Upfront option does not require any upfront payment and provides a discounted hourly rate for the duration of the term.

Question 18

When are RIs activated?

Reserved Instances

Amazon EC2 | Compute

Answer 18

The billing discount and capacity reservation (if applicable) is activated once your payment has successfully been authorized. You can view the status (pending | active | retired) of your RIs on the “Reserved Instances” page of the Amazon EC2 Console.

Question 19

Do RIs apply to Spot instances or instances running on a Dedicated Host?

Reserved Instances

Amazon EC2 | Compute

Answer 19

No, RIs do not apply to Spot instances or instances running on Dedicated Hosts. To lower the cost of using Dedicated Hosts, purchase Dedicated Host Reservations.

Question 20

How do RIs work with Consolidated Billing?

Reserved Instances

Amazon EC2 | Compute

Answer 20

Our system automatically optimizes which instances are charged at the discounted rate to ensure that the consolidated accounts always pay the lowest amount. If you own RIs that apply to an Availability Zone, then only the account which owns the RI will receive the capacity reservation. However, the discount will automatically apply to usage in any account across your consolidated billing family.

Question 21

Can I get a discount on RI purchases?

Reserved Instances

Amazon EC2 | Compute

Answer 21

Yes, EC2 provides tiered discounts on RI purchases. These discounts are determined based on the total list value (non-discounted price) for the active RIs you have per region. Your total list value is the sum of all expected payments for an RI within the term, including both the upfront and recurring hourly payments. The tier ranges and corresponding discounts are shown alongside.

Tier Range of List Value

Discount on Upfront

Discount on Hourly

Less than $500k

0%

0%

$500k-$4M

5%

5%

$4M-$10M 10% 10%

More than $10M Call Us

Question 22

Can you help me understand how volume discounts are applied to my RI purchases?

Reserved Instances

Amazon EC2 | Compute

Answer 22

Sure. Let’s assume that you currently have $400,000 worth of active RIs in the US-east-1 region. Now, if you purchase RIs worth $150,000 in the same region, then the first $100,000 of this purchase would not receive a discount. However, the remaining $50,000 of this purchase would be discounted by 5 percent, so you would only be charged $47,500 for this portion of the purchase over the term based on your payment option.

To learn more, please visit the Understanding Reserved Instance Discount Pricing Tier portion of the Amazon EC2 User Guide.

Question 23

How do I calculate the list value of an RI?

Reserved Instances

Amazon EC2 | Compute

Answer 23

Here is a sample list value calculation for three-year Partial Upfront Reserved Instances:

3yr Partial Upfront Volume Discount Value in US-East

Upfront $

Recurring Hourly $

Recurring Hourly Value

List Value

m3.xlarge

$ 1,345

$ 0.060

$ 1,577

$ 2,922

c3.xlarge

$ 1,016

$ 0.045

$ 1,183

$ 2,199

Question 24

How are volume discounts calculated if I use Consolidated Billing?

Reserved Instances

Amazon EC2 | Compute

Answer 24

If you leverage Consolidated Billing, AWS will use the aggregate total list price of active RIs across all of your consolidated accounts to determine which volume discount tier to apply. Volume discount tiers are determined at the time of purchase, so you should activate Consolidated Billing prior to purchasing RIs to ensure that you benefit from the largest possible volume discount that your consolidated accounts are eligible to receive.

Question 25

Do Convertible RIs qualify for Volume Discounts?

Reserved Instances

Amazon EC2 | Compute

Answer 25

No, however the value of each Convertible RI that you purchase contributes to your volume discount tier standing.

Question 26

How do I determine which volume discount tier applies to me?

Reserved Instances

Amazon EC2 | Compute

Answer 26

To determine your current volume discount tier, please consult the Understanding Reserved Instance Discount Pricing Tiers portion of the Amazon EC2 User Guide.

Question 27

Will the cost of my RIs change, if my future volume qualifies me for other discount tiers?

Reserved Instances

Amazon EC2 | Compute

Answer 27

No. Volume discounts are determined at the time of purchase, therefore the cost of your RIs will continue to remain the same as you qualify for other discount tiers. Any new purchase will be discounted according to your eligible volume discount tier at the time of purchase.