Amazon EC2 Auto Scaling

Amazon EC2 Auto Scaling helps you ensure that you have the correct number of Amazon EC2 instances available to handle the load for your application. You create collections of EC2 instances, called Auto Scaling groups. You can specify the minimum number of instances in each Auto Scaling group, and Amazon EC2 Auto Scaling ensures that your group never goes below this size.

You can specify the maximum number of instances in each Auto Scaling group, and Amazon EC2 Auto Scaling ensures that your group never goes above this size. If you specify the desired capacity, either when you create the group or at any time thereafter, Amazon EC2 Auto Scaling ensures that your group has this many instances. If you specify scaling policies, then Amazon EC2 Auto Scaling can launch or terminate instances as demand on your application increases or decreases.

For example, the following Auto Scaling group has a minimum size of one instance, a desired capacity of two instances, and a maximum size of four instances. The scaling policies that you define adjust the number of instances, within your minimum and maximum number of instances, based on the criteria that you specify.

For more information about the benefits of Amazon EC2 Auto Scaling, see Amazon EC2 Auto Scaling benefits.

The following table describes the key components of Amazon EC2 Auto Scaling.

| GroupsYour EC2 instances are organized into groups so that they can be treated as a logical unit for the purposes of scaling and management. When you create a group, you can specify its minimum, maximum, and, desired number of EC2 instances. For more information, see Auto Scaling groups.

| Configuration templatesYour group uses a launch template, or a launch configuration (not recommended, offers fewer features), as a configuration template for its EC2 instances. You can specify information such as the AMI ID, instance type, key pair, security groups, and block device mapping for your instances. For more information, see Launch templates and Launch configurations.

| Scaling optionsAmazon EC2 Auto Scaling provides several ways for you to scale your Auto Scaling groups. For example, you can configure a group to scale based on the occurrence of specified conditions (dynamic scaling) or on a schedule. For more information, see Scaling options.

There are no additional fees with Amazon EC2 Auto Scaling, so it's easy to try it out and see how it can benefit your AWS architecture. You only pay for the AWS resources (for example, EC2 instances, EBS volumes, and CloudWatch alarms) that you use.