Identifying optimal locations for flexible workloads with Spot placement score

This post is written by Jessie Xie, Solutions Architect for EC2 Spot, and Peter Manastyrny, Senior Product Manager for EC2 Auto Scaling and EC2 Fleet.

Amazon EC2 Spot Instances let you run flexible, fault-tolerant, or stateless applications in the AWS Cloud at up to a 90% discount from On-Demand prices. Since we introduced Spot Instances back in 2009, we have been building new features and integrations with a single goal – to make Spot easy and efficient to use for your flexible compute needs.

Spot Instances are spare EC2 compute capacity in the AWS Cloud available for steep discounts. In exchange for the discount, Spot Instances are interruptible and must be returned when EC2 needs the capacity back. The location and amount of spare capacity available at any given moment is dynamic and changes in real time. This is why Spot workloads should be flexible, meaning they can utilize a variety of different EC2 instance types and can be shifted in real time to where the spare capacity currently is. You can use Spot Instances with tools such as EC2 Fleet and Amazon EC2 Auto Scaling which make it easy to run workloads on multiple instance types.

The AWS Cloud spans 81 Availability Zones across 25 Regions with plans to launch 21 more Availability Zones and 7 more Regions. However, until now there was no way to find an optimal location (either a Region or Availability Zone) to fulfill your Spot capacity needs without trying to launch Spot Instances there first. Today, we are excited to announce Spot placement score, a new feature that helps you identify an optimal location to run your workloads on Spot Instances. Spot placement score recommends an optimal Region or Availability Zone based on the amount of Spot capacity you need and your instance type requirements.

Spot placement score is useful for workloads that could potentially run in a different Region. Additionally, because the score takes into account your instance type selection, it can help you determine if your request is sufficiently instance type flexible for your chosen Region or Availability Zone.

How Spot placement score works

To use Spot placement score you need to specify the amount of Spot capacity you need, what your instance type requirements are, and whether you would like a recommendation for a Region or a single Availability Zone. For instance type requirements, you can either provide a list of instance types, or the instance attributes, like the number of vCPUs and amount of memory. If you choose to use the instance attributes option, you can then use the same attribute configuration to request your Spot Instances in the recommended Region or Availability Zone with the new attribute-based instance type selection feature in EC2 Fleet or EC2 Auto Scaling.

Spot placement score provides a list of Regions or Availability Zones, each scored from 1 to 10, based on factors such as the requested instance types, target capacity, historical and current Spot usage trends, and time of the request. The score reflects the likelihood of success when provisioning Spot capacity, with a 10 meaning that the request is highly likely to succeed. Provided scores change based on the current Spot capacity situation, and the same request can yield different scores when ran at different times. It is important to note that the score serves as a guideline, and no score guarantees that your Spot request will be fully or partially fulfilled.

You can also filter your score by Regions or Availability Zones, which is useful for cases where you can use only a subset of AWS Regions, for example any Region in the United States.

Let’s see how Spot placement score works in practice through an example.

Using Spot placement score with AWS Management Console

To try Spot placement score, log into your AWS account, select EC2, Spot Requests, and click on Spot placement score to open the Spot placement score window.

Here, you need provide your target capacity and instance type requirements by clicking on Enter requirements. You can enter target capacity as a number of instances, vCPUs, or memory. vCPUs and memory options are useful for vertically scalable workloads that are sized for a total amount of compute resources and can utilize a wide range of instance sizes. Target capacity is limited and based on your recent Spot usage with accounting for potential usage growth. For accounts that do not have recent Spot usage, there is a default limit aligned with the Spot Instances limit.

For instance type requirements, there are two options. First option is to select Specify instance attributes that match your compute requirements tab and enter your compute requirements as a number of vCPUs, amount of memory, CPU architecture, and other optional attributes. Second option is to select Manually select instance types tab and select instance types from the list.

Please note that you need to select at least three different instance types (that is, different families, generations, or sizes). If you specify a smaller number of instance types, Spot placement score will always yield a low score. Spot placement score is designed to help you find an optimal location to request Spot capacity tailored to your specific workload needs, but it is not intended to be used for getting high-level Spot capacity information across all Regions and instance types.

Let’s try to find an optimal location to run a workload that can utilize r5.8xlarge, c5.9xlarge, and m5.8xlarge instance types and is sized at 2000 instances.

Once you select 2000 instances under Target capacity, select r5.8xlarge, c5.9xlarge, and m5.8xlarge instances under Select instance types, and click Load placement score button, you will get a list of Regions sorted by score in a descending order. There is also an option to filter by specific Regions if needed.

The highest rated Region for your requirements turns out to be US East (N. Virginia) with a score of 8. The second closest contender is Europe (Ireland) with a score of 5. That tells you that right now the optimal Region for your Spot requirements is US East (N. Virginia).

Let’s now see if it is possible to get a higher score. Remember, the key best practice for Spot is to be flexible and utilize as many instance types as possible. To do that, press the Edit button on the Target capacity and instance type requirements tab. For the new request, keep the same target capacity at 2000, but expand the selection of instance types by adding similarly sized instance types from a variety of instance families and generations, i.e., r5.4xlarge, r5.12xlarge, m5zn.12xlarge, m5zn.6xlarge, m5n.8xlarge, m5dn.8xlarge, m5d.8xlarge, r5n.8xlarge, r5dn.8xlarge, r5d.8xlarge, c5.12xlarge, c5.4xlarge, c5d.12xlarge, c5n.9xlarge. c5d.9xlarge, m4.4xlarge, m4.16xlarge, m4.10xlarge, r4.8xlarge, c4.8xlarge.

After requesting the scores with updated requirements, you can see that even though the score in US East (N. Virginia) stays unchanged at 8, the scores for Europe (Ireland) and US West (Oregon) improved dramatically, both raising to 9. Now, you have a choice of three high-scored Regions to request your Spot Instances, each with a high likelihood to succeed.

To request Spot Instances based on the score, you can use EC2 Fleet or EC2 Auto Scaling. Please note, that the score implies that you use capacity-optimized Spot allocation strategy when requesting the capacity. If you use other allocation strategies, such as lowest-price, the result in the recommended Region or Availability Zone will not align with the score provided.

You can also request the scores at the Availability Zone level. This is useful for running workloads that need to have all instances in the same Availability Zone, potentially to minimize inter-Availability Zone data transfer costs. Workloads such as Apache Spark, which involve transferring a high volume of data between instances, would be a good use case for this. To get scores per Availability Zone you can check the box Provide placement scores per Availability Zone.

When requesting instances based on Availability Zone recommendation, you need to make sure to configure EC2 Fleet or EC2 Auto Scaling request to only use that specific Availability Zone.

With Spot placement score, you can test different instance type combinations at different points in time, and find the most optimal Region or Availability Zone to run your workloads on Spot Instances.

Availability and pricing

You can use Spot placement score today in all public and AWS GovCloud Regions with the exception of those based in China, where we plan to release later. You can access Spot placement score using the AWS Command Line Interface (CLI), AWS SDKs, and Management Console. There is no additional charge for using Spot placement score, you will only pay EC2 standard rates if provisioning instances based on recommendation.

To learn more about using Spot placement score, visit the Spot placement score documentation page. To learn more about best practices for using Spot Instances, see Spot documentation.