ApsaraDB RDS:Create a disaster recovery instance (set up a disaster recovery instance group)

Key concepts

Before you begin, you must understand the following concepts:

• Disaster recovery instance group: A disaster recovery instance group consists of a primary instance and a disaster recovery instance in a one-to-one architecture. For more information, see Architecture.

• Primary instance: The primary instance is the primary role in the disaster recovery instance group. It handles read and write requests and synchronizes data to the disaster recovery instance in real time.

• Disaster recovery instance: The disaster recovery instance is the secondary role in the disaster recovery instance group and serves several purposes:

  • Remote disaster recovery: The disaster recovery instance acts as a remote disaster recovery node for the primary instance. If the primary instance fails or its region becomes unavailable, you can use the disaster recovery instance to quickly recover your services. This ensures data security and business continuity.

  • Remote read-only access: The disaster recovery instance supports read-only access, which offloads query pressure from the primary instance. This feature is suitable for multi-region deployments and read/write splitting scenarios. It enables local access for business applications and reduces data access latency.

  • Fast data migration: You can quickly migrate business data to other regions by promoting the disaster recovery instance to the primary role.

Prerequisites

If you are using a disaster recovery instance group for the first time, you must first authorize DTS to access cloud resources.

Limits

Notes

• A disaster recovery instance group can contain only one primary instance and one disaster recovery instance.

• An ApsaraDB RDS for SQL Server instance can be added to only one disaster recovery instance group, either as a primary instance or a disaster recovery instance. An instance cannot be added to multiple disaster recovery instance groups.

• Databases and accounts that are created on the primary instance are synchronized to the disaster recovery instance. However, privileged accounts on the primary instance become standard accounts after they are synchronized to the disaster recovery instance.

Billing

When you create a disaster recovery instance, the system automatically configures the primary instance and the disaster recovery instance to form a disaster recovery instance group. For more information about billing, see Billing.

• If you create a disaster recovery instance group with a new RDS instance, you are charged for the new RDS instance and for DTS data synchronization.

• If you create a disaster recovery instance group with an existing instance, you are not charged an additional instance fee, but you are charged for data synchronization.

Method 1: Create a new instance and add it as a disaster recovery instance

Method 2: Add an existing instance as a disaster recovery instance

You can add an existing ApsaraDB RDS for SQL Server instance to a disaster recovery instance group as a disaster recovery instance. The existing instance must meet the limits described in this topic.

1. Create a disaster recovery instance group

   1. Go to the Global Active Instances page and click Create Instance Group.

   2. On the Create Global Active Instance Group page, configure the following parameters and click OK.

      Configuration item	Description
      Instance Group Name	Enter a custom name for the instance group. We recommend that you use a name that is related to your business or purpose for easy identification. Naming conventions: The name must start with an uppercase letter, a lowercase letter, or a Chinese character. It can contain digits, underscores (_), and hyphens (-). The name must be 2 to 126 characters in length.
      Database Instance Type	Select SQL Server.
      Instance Group Type	Disaster Recovery: Suitable for cross-region disaster recovery and disaster recovery drill scenarios. The primary role is read-write, the secondary role is read-only, and it supports primary/secondary switchover and promotion.
      Region of Primary Instance	This is the same as the region selected in the RDS console. To select a different region, change the region at the top of the console.
      Primary Instance	From the drop-down list, select an RDS for SQL Server instance in the primary role region. If no primary role instances are available in the current region, you can click Create Primary Instance to go to the instance purchase page and create a primary instance.

2. Add the existing instance as a disaster recovery instance

   1. Go to the RDS Instances page. In the top navigation bar, select the region where the target disaster recovery instance resides. Then, click the ID of the instance.

   2. Click Add to GAD Cluster in the upper-right corner of the page.

   3. In the dialog box that appears, verify the information of the disaster recovery instance, which is the secondary role, and select the disaster recovery instance group that you created in the previous step.

      

   4. Click Check. After all precheck items pass, verify the data synchronization fee on the page and click OK in the lower-right corner of the page.

      You are redirected to the details page of the disaster recovery instance group. The system automatically creates a one-way DTS data synchronization link.

      • The system creates a data synchronization link between the primary instance and the disaster recovery instance. During this process, the instance group status is Creating Data Synchronization Task.

      • After the instance group status changes to Running, you can view related data on the disaster recovery instance group details page, such as the disaster recovery instance and the performance of the disaster recovery data synchronization link.

Related operations

• View disaster recovery instance group details

• Switch between a disaster recovery instance and a primary instance

• Promote a disaster recovery instance to a primary instance