RDS High-availability Edition

RDS High-availability Edition is a general-purpose cloud database edition. It uses a classic high-availability architecture with a primary instance and a secondary instance, and is suitable for more than 80% of user scenarios across various industries, including the internet, IoT, retail e-commerce, logistics, and gaming.

Topology

Benefits

• High availability

  Based on the parameter template that you select, data is replicated from the primary instance to the secondary instance in semi-synchronous or asynchronous mode. If the primary instance fails, the system automatically fails over to the secondary instance.

  The primary and secondary instances can be deployed in the same or different availability zones within the same region. Deploying them in different availability zones enables cross-zone disaster recovery and improves instance availability.

  Note

  • If the secondary instance fails, the system creates a new backup of the primary instance. As the backup nears completion, the system applies a global lock (FTWRL) to the primary instance, making it read-only for a short period, typically no more than 5 seconds.

  • When the instance uses the default parameter template, the data replication mode is semi-synchronous: After the primary instance completes an update, it synchronously sends the logs to the secondary instance. A transaction is considered committed once the secondary instance acknowledges receipt of the logs, without waiting for the secondary instance to replay the logs. If the secondary instance becomes unavailable or a network issue occurs between the primary and secondary instances, the semi-synchronous mode degrades to asynchronous mode.

  • When the instance uses the asynchronous or high-performance parameter template, the data replication mode is asynchronous: When an application initiates an update request, such as an insert, delete, or update operation, the primary instance responds immediately after completing the operation and then asynchronously replicates the data to the secondary instance. In asynchronous mode, the unavailability of the secondary instance does not affect operations on the primary instance. However, if the primary instance fails, data inconsistency may occur between the two instances.

• Comprehensive features

  RDS High-availability Edition instances offer a full range of features, including auto scaling, backup and restore, performance optimization, and read/write splitting. They also provide the SQL Explorer feature, which can store all SQL execution records for up to five years. This enables auditable database access and ensures the security of your core data.

Limitations

For performance reasons, the primary and secondary instances cannot be deployed across regions.

Upgrade to RDS High-availability Edition

RDS Basic Edition instances do not have a secondary instance for hot standby. This can lead to extended downtime during unexpected instance failures or maintenance tasks such as configuration changes and version upgrades. If your business requires high database availability, consider using RDS High-availability Edition.

Create an instance

FAQ

• Can I connect to the secondary instance?

  No. You can connect only to the primary instance. The secondary instance serves only as a standby and is not accessible to your applications.

• Can I downgrade an RDS High-availability Edition instance to RDS Basic Edition?

  No, you cannot directly downgrade to RDS Basic Edition. You can purchase an RDS Basic Edition instance, migrate data to the new instance, and then release the original instance.

• How do I change the data replication mode for an RDS High-availability Edition instance?

  See Query and change the data replication mode.

• If the secondary instance cannot keep up with the primary instance, does the data replication mode degrade to asynchronous mode?

  Yes. For more information, see Data replication modes.