Best Practices for Optimizing Amazon EC2 Spot Instances usage – Part 1

Overview

Spot Instances allow us to leverage idle Amazon EC2 capacity in AWS and are available for up to 90% off On-Demand pricing. Spot Instances allow us to leverage AWS’s massive operating scale to deploy hyperscale workloads for a fraction of the cost. In exchange for these discounts, AWS can reclaim the Spot Instances whenever Amazon EC2 requires the capacity. Amazon Web Services (AWS) offers a two-minute timeout before recovering Spot Instances, so workloads running on these instances can be automatically terminated.

Introduction

Amazon EC2 offers on-demand and scalable compute in the AWS Cloud. With Amazon EC2, we’ll save on hardware costs, allowing us to develop and deploy faster.

In this blog post, we have outlined best practices to maximize the utilization of Spot Instances and reduce the impact of spot instance interruptions: diversification, instance type selection based on attributes, utilization of spot placement scores, and allocation strategy based on price-capacity optimization. By implementing these best practices, users can utilize Spot Instances for the right workloads and reduce their compute costs. The blog will focus on integrating Spot Instances with the Amazon EC2 Autoscaling groups.

Pre-requisites

Amazon Spot Instances are available for many stateless, fault tolerant, or flexible applications, including Big data, Containers, CI/CD, Web Servers, High-Performance Computing (HPC), and AI/ML workloads. Note: As mentioned above, AWS can interrupt a Spot Instance with a 2-minute notice, so it’s best to avoid using a Spot Instance for workloads that can’t handle individual instance interruption, i.e., inflexible, Stateful, Fault tolerant, or tightly coupled.

Best Practices

1. Diversify Instances: When it comes to Spot Instances, flexibility is one of the most important things to consider. Spot capacity pool is a set of unused Amazon EC2 instances of the same type (for example, m7i.large) within the same AWS Region or Availability Zone (e.g., us-west-1b). When we apply for a Spot Instance, we ask for instances from a particular pool of Amazon EC2 capacity. Because Spot Instances are Amazon EC2 instances, we want to use as many of the available pools of capacity as we can to maximize our chances of getting them. We should diversify across instance sizes, instance types, generations, and Availability Zones to maximize the savings with Spot instances. For example, suppose we are using c3a.large in us-west-1a. In that case, we should consider including the c5a instances (a newer generation of instances), c3a.xl (large size), or a different Availability Zone us-west-1b to increase our overall flexibility. Instance diversification is useful for choosing Spot Instances and scalability, resilience, and cost reduction.
2. Consider attribute-based instance type selection:
   We’ve learned that flexibility is the key to optimizing your Spot Instances. We’ve also figured out that we should choose multiple instance types if we want to get the Spot Instances capacity we need. It might seem like a lot of work to set up and keep track of different instances, but it doesn’t have to be! With an attribute-based selection of instance types, you can specify the attributes of each type – e.g., memory, CPU, and storage – and with Amazon EC2 Auto Scaling, instances that match your defined attributes will be automatically launched. This eliminates the need to configure and update instance types manually. Additionally, this selection method allows you to automatically deploy newly launched instance types as they are available, so you can always access an ever-expanding range of SP capacity. Attribute based instance type selection is great for workloads or frameworks that are instance-agnostic, such as high-performance computing (HPC) workloads or big data workloads. It can also help to reduce the burden of manually choosing instance types to meet particular requirements.

How to figure out the prices and pick the best spot instances?

The spot instance pricing for AWS can be found on both the spot instance pricing page and the spot instance advisor page. These resources can assist in determining the potential cost savings compared to Amazon EC2 pricing on demand.

When selecting a spot instance price, bidding higher than the default on-demand price is not advantageous. AWS determines the price based on overall market trends rather than specific, real-time bids. Additionally, AWS spot instance interruptions are determined by AWS without any correlation to the bid price. Therefore, leaving the maximum price at the default setting established by AWS is recommended.

How can you get the historical pricing of spot instances?

However, suppose you have a particular budget in mind, either below the on-demand rate or even lower than the current spot instance rate. In that case, you may refer to the historical spot instance prices and indicate your preferred price. This approach ensures that your Amazon EC2 spot instance will only be activated when the prevailing market price corresponds to your specified bid or falls below it.

To view spot price data, kindly follow the steps below:

• Launch the Amazon EC2 console and navigate to the Spot Requests section.
• Opt for the Pricing History option.
• Choose a product (operating system), date range, instance type, and price history are displayed. Hovering the pointer over the chart to see price trends over time.

Conclusion

Spot Instances offers cost-effective solutions for various applications, including containers, large-scale data storage, machine learning, high-performance computing (HPC), and CI/CD. In this blog, we have discussed two Spot Instances best practices that can help us optimize your Spot Instance usage to maximize savings:
‘Diversifying your instances’ & ‘Considering the attribute based instance types selection’. In the next part of this blog, we will discuss ‘Leverage Spot placement’ & ‘Use of the price-capacity-optimized allocation strategy’.

Click here for Part 2.

Drop a query if you have any questions regarding Amazon EC2 and we will get back to you quickly.

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