Amazon Elastic Compute Cloud (EC2) is a cloud computing service that instantly provides flexible and scalable resources to deploy virtual servers, called instances. While Spot Instances can save you a significant amount of money, especially for short-lived workloads, there may come a time when you need a more predictable pricing model. This is where Reserved Instances (RIs) come in handy. In this article, we’ll explain the reasons for switching from a Spot Instance to a Reserved Instance and guide you through the process.

Understanding Spot Instances and Reserved Instances:

Spot Instances and Reserved Instances are two pricing models available on Amazon EC2. Spot Instances are cost-effective for workloads that can handle interruptions and have flexible running schedules. Users can bid on spare EC2 capacity to use them at a lower cost. On the other hand, Reserved Instances provide users with capacity reservations for a period of one or three years, offering a significant discount compared to On-Demand Instances.

Reasons to Switch:

1. Cost Predictability:

   • • Spot Instances are subject to market pricing and can experience sudden termination if the market price exceeds your bid. Reserved Instances provide a fixed, predictable cost, making it easier to budget for your infrastructure expenses.

2. Stability and Availability:

   • • Reserved Instances provide a higher level of availability and stability compared to Spot Instances. The latter can be terminated if the spot price exceeds the bid, which is crucial for applications requiring constant availability and minimal interruptions.

3. Long-Term Commitments:

   • • If you have a workload with a predictable and steady resource usage over an extended period, a Reserved Instance can be a more cost-effective option.

Switching from Spot to Reserved Instances:

1. Evaluate Your Workload:

   • • Before switching to Spot Instances, evaluate your workload to identify if it requires continuous availability and if the cost savings outweigh the potential interruptions. 

2. Select the Right Reserved Instance:

   • • Purchase Reserved Instances based on your workload’s characteristics, such as instance type, region, and term length (one or three years). Use the AWS Pricing Calculator to estimate cost savings.

3. Purchase the Reserved Instances:

   • • Once you’ve identified the right Reserved Instances, proceed to the AWS Management Console or use the AWS Command Line Interface (CLI) to purchase them. Ensure that the purchased Reserved Instances match the specifications of your existing Spot Instances.

4. Monitor and Optimize:

   • • Regularly monitor your new Reserved Instances and optimize your usage based on changing requirements. You can adjust the number and type of Reserved Instances to align with your workload’s evolving needs.

Steps for switching your Spot instance to Reserved Instance

Purchasing Reserved Instances

1. Go to the Reserved instances under the Instances option and select Purchase Reserved Instances.
2. Input the required details for the reserved instance to be purchased and click search. If you have found the desired instance type, add it to the cart.
3. To see a summary of the Reserved Instances that you selected, choose View Cart, then proceed to click Order All to purchase the RI.

Final Thoughts:

If you have a workload with predictable resource requirements and need stability and cost predictability, switching from Spot Instances to Reserved Instances on Amazon EC2 can be an excellent strategic move. To make the transition seamless, you should evaluate your workload carefully, choose the right Reserved Instances, and follow the migration steps. Keep in mind that AWS offers different pricing models, and selecting the one that aligns with your specific workload characteristics is essential for optimizing costs and performance in the cloud.