Reserved instances ＆ Savings Plans

Today we'll see two in AWS It is very important in the field of cost management and optimization , And it is particularly easy to confuse the billing method  -  Reserved instance （Reserved instances） And saving plan （Savings Plans）. When we start using AWS Computing resources in , The default billing method is pay as you need . If you are only short-term , Use... Sparingly , Then the cost of this billing method is acceptable . But if it is used in large quantities for a long time , Then the price of pay as you need is not so advantageous . At this time, you can consider using reserved instances or savings plans to provide preferential discounts , To help you increase revenue and reduce expenditure , So as to go to the cloud in a more cost-effective way .

Single from AWS The definitions of these two billing methods in the document , It's hard to understand what they mean , I haven't been clear about this problem before . These two days I spent a little time to study it again , Finally, I basically understood the specific contents and differences between the two services .

Reserved instance

The reserved instance method can only be used for Amazon EC2. Compared to pay as you need , It can provide 72% Discount on . Note that this method is used every day 24 Calculate the billing discount on the premise of hours , That is, whether you actually use it every day or not 24 Hours , It all uses 24 Hours as the daily billing time . Reserved instances have two purchase terms, one-year and three-year , The corresponding discount is also different . Of course , The three-year discount must be bigger . in addition , There are three different ways to pay ：

• No prepayment  -  There is no need to pay in advance , Minimum discount

• Partial prepayment  -  Pay part of the money in advance , Discount is better than no prepayment

• Full prepayment  -  Pay all the money in advance , The biggest discount

Reserved instance range

When purchasing reserved instances , You need to determine the scope of reserved instances . The scope can be regional （Regional） Or the availability zone （Zonal）. Scope does not affect pricing , The price of reserved instances in the region and the availability zone is the same .

Reserved instance level

In the reserved instance mode , You can do as you need EC2 Type of instance （instance type） Choose the following two purchase levels ：

• Standard grade （Standard）-  You can specify one Amazon EC2 Instance types enjoy preferential discounts , such as c4.large Instance type , If you use other types of instances , You will not enjoy the discount offered by the reserved instance program . You can modify the instance type according to business needs , But you cannot exchange with other reserved instances . The standard grade can enjoy the maximum discount .

• Exchangeable grade （Convertible）-  If you have more than one Convertible Reserved instance , They can be exchanged according to business needs , But the exchange needs to meet the following conditions ： The attribute value of the target reserved instance （ Generally refers to the instance type ） Must be higher than or equal to the original reserved instance .Convertible Reserved instances also support modifying instance types . Give an example for understanding ： Suppose you buy something that includes 100 individual c4.medium Of Convertible Reserve instances and 50 individual c4.large Of Covertible Reserved instance . After a period of time, you find that you need more c4.large And you don't have to c4.medium, Then you can choose to c4.medium The reserved instance of is converted to c4.large Reserved instances of ,AWS It will help you calculate the number of final conversions .

Reserve the business type suitable for the instance

It's not hard to see. , The reserved instance method is more suitable for businesses that do not allow interruption or can only be interrupted occasionally , And the business demand is predictable and relatively stable for a period of time . For specific pricing of reserved instances, please refer to the official website

https://aws.amazon.com/cn/ec2/pricing/reserved-instances/pricing/

With US East Buy three-year installation in Ohio Linux Systematic a1.medium Take reserved instances as an example , The following figure shows the cost details of standard level and convertible level respectively ：

Standard grade

Convertible grade

Saving plan

Although reserving instances can save money compared with paying on demand , But its limitations are also obvious ：

• The billing duration is fixed to every day 24 Hours . That is, whether you actually use it every day or not 24 Hours , It takes every day 24 The hourly usage is charged . This is obviously still a little rough ,

• Only applicable to Amazon EC2 example . With AWS More computing services have been launched on , More and more users may not only use EC2 As a workload .

Based on the above two obvious disadvantages ,AWS After that, another preferential billing method was introduced  -  Saving plan （Savings Plans）.

In this way , The necessary condition for enjoying the discount is to promise to use a certain amount , In US dollars / Hour is the measure . That is to say, you should promise one hourly rate, You can enjoy a certain discount . If it doesn't reach, it will be promised hourly rate To calculate , If the excess part , Then pay as you need . Simply describing concepts may still be a little abstract , We can give a general example ： If your business load needs to run every month 100 Hours , Total cost 400 dollar , So your hourly rate Namely 4 dollar / Hours . So this one 4 dollar / Hours can be used as a promised amount （commit usage） Buy a savings plan ,AWS Can give you a discount , such as 6 fold , That is to say 2.4 dollar / Hours . If the business load runs next month 120 Hours , The total cost is 500 dollar , Then according to the 4 dollar / Hours of hourly rate,120 The cost of hours should be 480 dollar , this 480 Dollars can enjoy 6 fold , And beyond 20 Dollars is paid at the original price .

Another flexibility of the savings plan is that it eliminates the need to apply only to EC2 The limitation of , By providing three types of Savings Plans, It can cover more AWS service . These three types are ：

• Compute Savings Plans -  Can be used for Amazon EC2（ Include EMR,ECS and EKS Inside EC2）,AWS Lambda,AWS Fargate. Up to... Can be provided 66% A discount of .

• EC2 Instance Savings Plans -  Only applicable to specified EC2 Instance type , But the maximum discount can reach 72%.

• Amazon SageMaker Savings Plan -  Apply to Amazon SageMaker, You can save at most 64% The cost of .

Just like reserved instances , The savings plan also has two purchase terms, one-year and three-year .

If you want more detailed information , Here's another one AWS Blog for your reference ：

New – Savings Plans for AWS Compute Services | AWS News Blog (amazon.com)