AWS EC2 Instance Types — On Demand Vs Reserved VS Spot? (Which one is best for your needs)

This article will explain the different type of options for procuring computing instances on the AWS cloud. This is critical information for anyone working with the AWS cloud, or preparing for AWS exams.

AWS primary computing platform is called Elastic Compute Cloud (EC2). EC2 servers are virtual machines launched on the AWS platform. EC2 servers are called instances. EC2 instances are sized like any virtualized server environment. AWS has numerous options to meet an organization’s needs. Instance types should be chosen based upon the need for the following computing options:

· CPU cores (virtual CPUs)

· Memory (DRAM)

· Storage (capacity and performance)

· Network performance

Key Drivers To Cloud Adoption

One of the key reasons’ organizations migrate to the cloud is agility. The ability to deploy a compute instance instantaneously, at the optimal size which can grow to meet the needs of the organization as needed. This can provide significant business benefits in metrics such as cost, capability but most importantly agility (or the ability to adapt) on demand. With these benefits comes the responsibility to choose the right computing platform in order to optimize costs. Choosing the proper instance type for the organization’s application can be the difference between a successful project and being vastly over budget.

Instance Purchasing Options

AWS has numerous options for purchasing computing instances. Each type of instance is optimized for different computing requirements. The type of computing instances available can be seen below:

· On-demand instances

· Reserved instances

· Scheduled reserved instances

· Spot instances

· Dedicated hosts

On-Demand Instances

On-demand computing instances are computing instances that are available when needed. On-demand instances are charged by either the second or hour of use, and facilitate autoscaling. This means these instances can grow on demand by adding additional instances. On-demand instances are optimal when reliable computing capacity is needed without complete knowledge of how long the application will be used or its capacity requirements.

Reserved Instances

A reserved instance is an instance where an organization commits to purchase a specified compute capacity for a specified period of time. It is essentially a contract to purchase a computing instance and can be for one to three years. By purchasing instances based upon long-term use, the organization can receive substantial savings over on-demand pricing. Reserved instances are optimal when an organization knows how long the application will be used and its capacity requirements.

Scheduled Reserved Instances

A scheduled reserved instance is a special type of reserved instance. This type of instance is optimal when you have a need for a specific amount of computing power on a scheduled basis. For example, if an organization has a mission-critical batch job that runs every Saturday and Sunday.

Spot Instances

A spot instance is an instance that is pulled from unused AWS capacity. Spot instances are sold in an auction-like manner in which an organization places a bid. If the bid price is equal to or greater than the spot price, a spot instance is purchased. Spot instances are deeply discounted and can be a great option. The drawback of spot instances is that they can be terminated if the spot price goes above the price that was bid on the instances. Spot instances are ideal when an organization needs extra computing capacity at a great price for non-mission-critical use.

Now you know the computing options avilable on the AWS cloud.

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