On-Demand vs Spot vs Reserved Instances on AWS
A basic articles on the differences between On-Demand and Spot Instances
Basic Introduction:
With On-Demand Instances, users can pay for computing resources on an hourly basis without making a long-term commitment. They are a fantastic option for users who need to swiftly scale their computing capacity up or down in response to changing or unpredictable workloads. Since they are based on scalable and highly accessible AWS infrastructure, on-demand instances are also a dependable option. They might, however, cost more in the long term than Reserved Instances or Spot Instances.
Spot Instances enable users to place bids on available Amazon EC2 computing resources, which can result in significant cost reductions. Users with flexible start and end timings and workloads that can be interrupted should use these instances. However, because Spot Instances are subject to termination at any time by Amazon EC2, they might not be appropriate for applications that need a high degree of continuity.
Reserved Instances offer discounted pricing in exchange for a one- or three-year commitment. There are two types of Reserved Instances: Standard Reserved Instances and Convertible Reserved Instances. Standard Reserved Instances offer the greatest discount, but they are specific to a certain instance type and region, and cannot be exchanged or returned. Convertible Reserved Instances offer a lower discount, but they can be exchanged for other instance types or regions, and can also be returned.
Key Advantages and Disadvantages
| Type | Advantage | Disadvantage |
| On-Demand | Users only pay for the computing capacity they use, which can be cost-effective for users with variable or unpredictable workloads. Another advantage is that there is no upfront payment or long-term commitment required, which makes it easy for users to get started with Amazon EC2. | They may be more expensive in the long run compared to Reserved Instances or Spot Instances, which offer discounted pricing in exchange for a longer commitment. On-Demand Instances may also not be suitable for users who have a consistent workload and can predict their compute capacity needs in advance. |
| Spot | They can provide significant cost savings compared to On-Demand Instances. They are also a good choice for users who have flexible start and end times, or for workloads that can be interrupted. | They can be terminated by Amazon EC2 at any time, so they may not be suitable for applications that require a high level of continuity. Another disadvantage is that the availability of Spot Instances can vary depending on the region and instance type, so it may be more difficult for users to predict their compute capacity needs in advance. |
| Reserves | They offer discounted pricing compared to On-Demand Instances. They are also a good choice for users who have a consistent workload and can predict their computing capacity needs in advance. | They require a long-term commitment, which may not be suitable for users who have variable or unpredictable workloads. |
Summary
In summary, the type of instance that is best for a user will depend on their specific needs and workloads. On-Demand Instances offer the convenience and flexibility of being able to pay for compute capacity on an hourly basis with no long-term commitment, while Reserved Instances and Spot Instances offer discounted pricing in exchange for a longer commitment. Users should carefully consider their compute capacity needs and workloads to choose the option that best meets their needs.
