Creating a Cross-AZ Replica Set Instance

You can deploy a replica set instance across three AZs. Multi-AZ replica set instances have higher DR capabilities than a single-AZ replica set instance and can withstand the impact caused by equipment room faults. To obtain higher DR capability, deploy resources across different AZs in the same region. If the AZ where the primary node is located fails due to power supply or network exceptions, the HA system automatically triggers a failover to ensure service continuity of a replica set instance.

This section describes how to create a replica set instance across AZs.

Precautions

Only some regions support multi-AZ replica set instances.
To create a multi-AZ instance, ensure that there are three or more AZs available in the region.
If an instance is deployed in multiple AZs, the primary, secondary, and hidden nodes of the instance are deployed in three different AZs.

Deployment Architecture Comparison

Single AZ
If an instance is deployed in a single AZ, the primary, secondary, and hidden nodes of the instance are deployed in the same AZ.

Figure 1 Single-AZ deployment
Multiple AZs
If an instance is deployed in multiple AZs, the primary, secondary, and hidden nodes of the instance are deployed in three different AZs for disaster recovery.

Figure 2 Multi-AZ deployment

Procedure

Log in to the management console.
Click in the upper left corner and select a region and a project.
Click in the upper left corner of the page and choose Databases > Document Database Service.
On the Instances page, click Buy DB Instance.
Configure the instance details and click Next.
- AZ: Select three AZs as shown in Figure 3.
  Figure 3 Selecting multiple AZs
- For details about other configuration items, see Buying a Replica Set Instance.
Confirm the order as prompted and complete the payment.