Help Center/ Elastic Cloud Server/ Drawer/ Purchasing an ECS/ Basic Configurations/ AZ
Updated on 2026-02-13 GMT+08:00
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AZ

Description

  • Availability zone (AZ)

    An AZ may have one or more physical data centers where resources have their own independent power supplies and networks. AZs are physically isolated but interconnected through an internal network.

    There are multiple AZs in each region. If one AZ becomes faulty, other AZs in the same region continue to provide services.

    Figure 1 shows the relationship between regions and AZs.

    Figure 1 Regions and AZs
  • Random

    If you set AZ to Random when creating ECSs, the cloud platform will allocate them to the AZs with the most available resources.

    The available ECS types and flavors vary by AZ. To view all supported ECS types and flavors on the cloud service platform, set AZ to Random. The system automatically allocates an AZ based on your selected ECS flavor.

    For example, suppose S6 ECSs are only available in AZ1; S3 ECSs are available for sale in AZ2 and AZ3, but they are sold out in AZ1. If you set AZ to Random, you can view both the S6 and S3 ECSs. If you purchase an S6 ECS, the system automatically allocates it to AZ1. If you purchase an S3 ECS, the system randomly allocates it to AZ2 or AZ3.

  • Randomly allocated to multiple AZs

    After you set AZ to Random, you can determine whether to select Randomly allocated to multiple AZs.

    • If you do not select this option, the cloud platform will allocate ECSs to a single AZ with the most appropriate capacity.
    • If you select this option, the cloud platform will allocate ECSs to multiple AZs based on the available capacity of each AZ.
      This setting does not apply when you purchase a single ECS. Instead, it applies to scenarios when the capacity of a single AZ is insufficient but the total capacity of multiple AZs is sufficient, to improve the ECS provisioning success rate.

      If you select Randomly allocated to multiple AZs and the available capacity of each AZ is sufficient, ECSs may also be allocated to a single AZ.

FAQs

Can ECSs in Different AZs Communicate with Each Other over a Private Network?

Yes. ECSs in different AZs of the same region can communicate with each other over a private network. ECSs in the AZs of different regions, however, cannot. You can assign EIPs to the ECSs to enable them to communicate with each other over the Internet.

How Do I Select an AZ?

When deploying resources, consider your application requirements for disaster recovery (DR) and network latency.

  • If your applications require robust DR capabilities, deploy resources in different AZs within the same region.
  • For lower network latency, deploy resources in the same AZ.

Can I Change the AZ Where My ECS Is Deployed?

No, you cannot change the AZ of an ECS.

If you want to migrate an ECS to another AZ, you can create a private image from the ECS and use the private image to create identical ECSs in the target AZ.

To do so, switch to the Elastic Cloud Server page, locate the target ECS and choose More > Manage Image > Create Image in the Operation column.

Parent Topic: Basic Configurations