What Are Regions and AZs?

Concepts

A region and availability zone (AZ) identify the location of a data center. You can create resources in a specific region and AZ.

• Regions are divided from the dimensions of geographical location and network latency. Public services, such as Elastic Cloud Server (ECS), Elastic Volume Service (EVS), Object Storage Service (OBS), Virtual Private Cloud (VPC), Elastic IP (EIP), and Image Management Service (IMS), are shared within the same region. Regions are classified as universal regions and dedicated regions. A universal region provides universal cloud services for common tenants. A dedicated region provides services of the same type only or for specific tenants.
• An AZ contains one or more physical data centers. Each AZ has independent cooling, fire extinguishing, moisture-proof, and electricity facilities. Within an AZ, computing, network, storage, and other resources are logically divided into multiple clusters. AZs within a region are interconnected using high-speed optical fibers to allow you to build cross-AZ high-availability systems.

Figure 1 shows the relationship between the regions and AZs.

Figure 1 Regions and AZs

Services are available in many regions around the world. You can select a region and AZ as needed.

How to Select a Region

When selecting a region, consider the following factors:

• Location

  You are advised to select a region close to you or your target users. This reduces the network latency and improves the access speed. Regions within the Chinese mainland provide the same infrastructure, BGP network quality, as well as resource operations and configurations. Therefore, if your target users are in the Chinese mainland, you do not need to consider the network latency differences when selecting a region.

  • If you or your target users are in Asia Pacific excepting the Chinese mainland, select the CN-Hong Kong, AP-Bangkok, or AP-Singapore region.
  • If you or your target users are in Africa, select the AF-Johannesburg region.
  • If you or your target users are in Europe, select the EU-Paris region.
• Relationship between cloud services

  When using multiple cloud services, pay attention to the following restrictions:

  • ECSs, RDS instances, and OBS buckets in different regions cannot communicate with each other through an internal network.
  • ECSs in different regions cannot be bound to the same load balancer.
• Resource price

  Resource prices may vary in different regions.

How to Select an AZ

When determining whether to deploy resources in the same AZ, consider your applications' requirements on disaster recovery (DR) and network latency.

• For high DR capability, deploy resources in different AZs in the same region.
• For low network latency, deploy resources in the same AZ.

Regions and Endpoints

Before using an API to call resources, specify its region and endpoint.