To ensure business continuity and high availability, ApsaraDB RDS for SQL Server provides a cross-region disaster recovery feature. This feature lets you create disaster recovery instances across regions.
Architecture
RDS for SQL Server provides a one-stop, cost-effective, cross-region disaster recovery solution based on SQL Server Distributed Availability Groups (DAG) and the cross-region network connectivity of DTS. A disaster recovery instance group uses a one-primary, one-secondary architecture. The primary instance supports read and write operations, and the secondary instance is read-only. The primary and secondary instances must have the same version number but can belong to different series. The instances are connected by a one-way data synchronization link that uses DAG and DTS to implement real-time data synchronization across regions. This ensures data consistency and provides a low-latency access experience. In a disaster recovery scenario, you can use the primary/secondary switchover or disaster recovery promotion features to quickly restore access to your application.
Scenarios: This feature is suitable for scenarios that require disaster recovery capabilities, such as cross-region disaster recovery and disaster recovery drills.
Limits
Category | Limits on primary instance | Limits on disaster recovery instance |
Region limits |
Note To deploy disaster recovery in other regions, you can submit a ticket. | |
Version and configuration limits | The primary instance must meet the following requirements:
Note If the major version of the primary instance is not supported, you must upgrade the major version. | The disaster recovery instance must meet the following requirements:
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Operation limits after a disaster recovery instance group is created |
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Billing
If you create a disaster recovery instance group by purchasing a new ApsaraDB RDS instance, you are charged an instance fee for the new instance and a data synchronization fee for DTS. If you add an existing instance to the group, you are charged only the data synchronization fee.
New RDS instance fees
When you purchase a new primary or disaster recovery RDS for SQL Server instance, you are charged for its specifications and storage. The supported billing methods are subscription and pay-as-you-go. The serverless billing method is not supported.
Data synchronization fees (free trial)
When you add a disaster recovery instance to an instance group, the system automatically creates a one-way data synchronization link between the primary and disaster recovery instances. You are charged a data synchronization fee based on the region and usage duration.
Data synchronization fee = Unit price of a one-way data synchronization link × Usage duration
Synchronization link
Unit price of a one-way synchronization link (USD/hour)
Synchronization within the Chinese mainland
0.187969924812
Synchronization between regions outside the Chinese mainland
(China (Hong Kong) and other regions)
0.375939849624
Synchronization between the Chinese mainland and regions outside the Chinese mainland
Not supported