Introduction
Amazon Elastic Compute Cloud (EC2) provides computing capacity in the AWS cloud, allowing you to launch virtual servers with a variety of operating systems. EC2 offers different pricing models, including On-Demand, Savings Plans, Reserved Instances, Spot Instances, and Dedicated Hosts, each designed to cater to different needs and usage patterns. Spot Instances can provide significant cost savings. Spot Instances are available at a discount of up to 90% off compared to On-Demand pricing.
This blog post will explore how Spot Instances and Spot Fleets work, their benefits, and some best practices for leveraging them effectively.
EC2 Instance Pricing Models Comparison
| Pricing Model | Description | Use Cases | Cost Optimization |
|---|---|---|---|
| On-Demand | Pay for compute capacity by the hour or second, only for what you use. No long-term commitments or upfront payments. | Short-term workloads, unpredictable spikes in demand, software development, and testing. | Right-size instances, use auto-scaling. |
| Savings Plans | Commit to a consistent amount of compute usage (measured in $/hour) for 1 or 3 years. Lower prices compared to On-Demand. | Steady-state usage, predictable workloads. | Choose the right Savings Plan type (Compute Savings Plan or EC2 Instance Savings Plan) for your workload. |
| Reserved Instances | Provide a capacity reservation and offer a significant discount on the hourly charge for EC2 instances. Contract terms of 1 or 3 years. | Applications with steady-state or predictable usage, require capacity reservations. | Evaluate utilization, consider convertible RIs for flexibility. |
| Spot Instances | Request spare EC2 capacity, paying up to 90% less than On-Demand prices. Instances can be interrupted with a two-minute warning. | Applications with flexible start and end times, urgent spikes in demand. Batch processing, CI/CD, data processing. | Use Spot Fleets for diversification, implement checkpointing for fault tolerance. |
| Dedicated Hosts | Physical EC2 servers dedicated for your use. Allows you to use your existing server-bound software licenses. | Regulatory requirements, licensing constraints. | Optimize instance utilization, consider AWS License Manager. |
What Are AWS Spot Instances?
Spot Instances allow you to request spare EC2 capacity, and pay significantly less (up to 90% off) the original on-demand price. Because they can be interrupted on short notice, spot instances are typically used for applications working at flexible start and end schedules, or to accommodate urgent spikes in demand for compute resources. The pricing of Spot Instances varies based on supply and demand.
Spot Instance prices are set by Amazon EC2 and adjust gradually based on long-term trends in supply and demand for Spot Instance capacity. Unlike On-Demand Instances, where you pay a fixed price per hour or second, Spot Instances involve a dynamic pricing mechanism.
What Are Spot Fleets?
Spot Fleets manage multiple Spot Instances dynamically. They offer auto-replacement, cost efficiency, and the ability to use mixed instance types. Spot Fleets are well-suited for batch processing, containerized workloads, and machine learning training. A Spot Fleet request includes the number of instances required, type of instances, the target capacity, and maximum price.
You decide on a maximum price you are willing to pay. Once the price set by AWS exceeds this threshold, Spot Fleets are terminated, typically with a two-minute grace period.
When & Where to Use Spot Instances?
Spot Instances are best suited for:
- Stateless applications
- CI/CD pipelines
- Data processing jobs
- Auto-scaling groups
However, avoid using Spot Instances for critical workloads that require guaranteed uptime.
How to Request & Manage Spot Instances?
To use Spot Instances, you must decide on your maximum spot price. The instance will be provisioned as long as the spot price is below your maximum bid. You can use Spot Fleet requests and EC2 Auto Scaling to manage your Spot Instances. It's crucial to set a maximum bid price and have a strategy for handling instance interruptions.
Handling Spot Interruptions Gracefully
AWS provides a two-minute notification before terminating a Spot Instance. You can use Instance Termination Notices and EC2 Hibernate to manage these interruptions. Strategies for handling interruptions include checkpointing, using Auto Scaling to replace interrupted instances, and falling back to On-Demand Instances if necessary.
Cost Optimization Tips for Spot Instances
- Combine On-Demand and Spot Instances in Auto Scaling groups.
- Leverage the Spot Instance Advisor for better pricing decisions.
Spot Instance Allocation Strategies
When using Spot Instances, you can employ different allocation strategies to optimize for cost and availability:
- Price-Capacity-Optimized: This strategy makes Spot allocation decisions based on both capacity availability and Spot prices.
- Lowest Price: While requesting Spot Instances, it's recommended to use the default maximum price, which is the On-Demand price.
- Diversified Instances: Spot Fleets let you select instances from different spot pools. EC2 tries to maintain the target capacity, adding spot instances if available, based on the request details.
Conclusion
Spot Instances and Spot Fleets provide a powerful way to reduce costs on AWS EC2. By understanding how they work and implementing best practices for managing them, you can take full advantage of the cost savings they offer.
Have you used Spot Instances before? Share your experience in the comments!
Top comments (0)