ApsaraDB for RDS offers four editions: Basic Edition, High-availability Edition, Cluster Edition, and Enterprise Edition. This topic describes the High-availability Edition.
In the High-availability Edition, data is synchronously replicated from the primary instance to the secondary instance. If the primary instance breaks down unexpectedly, your database system automatically fails over to the secondary instance.
You can deploy the primary and secondary instances in the same zone or in different zones.
The High-availability Edition supports all of the features that are provided by ApsaraDB for RDS. These features include automatic scaling, backup and restoration, performance optimization, read/write splitting, and SQL explorer. The SQL explorer feature allows you to query logs about the SQL statements executed. This makes database access traceable and ensures the security of important data.
You must deploy the primary and secondary instances in the same region for stable performance.
Upgrade to High-availability Edition
In the Basic Edition, the primary instance does not have a secondary instance as its hot backup. If the primary instance breaks down unexpectedly, is executing specification changes, or is updating its version, it may remain unavailable for a long period of time. If you have strict requirements for service availability, we recommend that you select the High-availability Edition.
- If your RDS instance is running MySQL 5.7, you can upgrade its edition from Basic to High-availability by changing the instance specifications. For more information, see Change the specifications of an ApsaraDB RDS MySQL instance.
- If your RDS instance is running SQL Server, you can upgrade its edition from Basic to High-availability in the ApsaraDB for RDS console. For more information, see Upgrade from Basic Edition to High-availability Edition.
- Can I access a secondary instance?
No, you cannot access a secondary instance. You can only access a primary instance. A secondary instance serves only as a backup and does not allow external access.
- Can I downgrade the edition of my RDS instance from High-availability to Basic?
No, you cannot downgrade the edition of your RDS instance from High-availability to Basic. You can create an RDS instance that runs the Basic Edition, migrate the data of your RDS instance to the new RDS instance, and then release your RDS instance. For more information, see Migrate data between RDS instances.