# What Is Auto Scaling?

#### AS Introduction

Auto Scaling (AS) helps you automatically scale Elastic Cloud Server (ECS) and bandwidth resources to keep up with changes in demand based on pre-configured AS policies. It allows you to add ECS instances or increase bandwidths to handle increases in load and also save money by removing resources that are sitting idle.

#### Architecture

AS allows you to scale ECS instances and bandwidths.

- Scaling control: You can configure AS policies, configure metric thresholds, and schedule when different scaling actions are taken. AS will trigger scaling actions on a repeating schedule, at a specific time, or when the configured thresholds are reached.
- Policy configuration: You can configure alarm-based, scheduled, and periodic policies as needed.
- Alarm-based policies: You can configure scaling actions to be taken when alarm metrics such as vCPU, memory, disk, and inbound traffic reaches the thresholds.
- Scheduled policies: You can schedule scaling actions to be taken at a specific time.
- Periodic policies: You can configure scaling actions to be taken at scheduled intervals, a specific time, or within a particular time range.
- When Cloud Eye generates an alarm for a monitoring metric, for example, CPU usage, AS automatically increases or decreases the number of instances in the AS group or the bandwidths.
- When the configured triggering time arrives, a scaling action is triggered to increase or decrease the number of ECS instances or the bandwidths.

Figure 1 AS architecture

#### Accessing AS

The public cloud provides a web-based service management platform. You can access AS using HTTPS-compliant application programming interfaces (APIs) or the management console.

- Calling APIs

  Use this method if you are required to integrate AS on the public cloud into a third-party system for secondary development. For details, see Auto Scaling API Reference.

- Management console

  Use this method if you do not need to integrate AS with a third-party system.

  After registering on the public cloud, log in to the management console and select Auto Scaling from the service list on the homepage.

Parent topic: Service Overview