ApsaraDB RDS offers four editions: Basic Edition, High-availability Edition, Cluster Edition, and Enterprise Edition. This topic describes the High-availability Edition.
The High-availability Edition is a popular edition that allows you to have one primary RDS instance and one secondary RDS instance in your database system. The primary and secondary RDS instances work in the classic high-availability architecture. This edition is suitable for more than 80% of the actual business scenarios. These scenarios include the Internet, Internet of Things (IoT), online retail, logistics, and gaming.
In the High-availability Edition, data is replicated from the primary RDS instance to the secondary RDS instance in semi-synchronous mode. If the primary RDS instance becomes faulty, your database system fails over to the secondary RDS instance.
You can deploy the primary and secondary RDS instances in the same zone or in different zones.
The High-availability Edition provides a complete suite of features. These features include automatic scaling, backup and restoration, performance optimization, read/write splitting, and SQL Explorer. The SQL Explorer feature allows you to store the logs of all executed SQL statements for up to five years. This makes database access behavior traceable and ensures the security of important data.
For performance purposes, you must deploy the primary and secondary RDS instances in the same region.
Upgrade to the High-availability Edition
The Basic Edition allows you to have only one primary RDS instance in your database system. In this case, the primary RDS instance does not have a secondary RDS instance as a hot standby. If the primary RDS instance exits unexpectedly, your database service becomes unavailable. If you change the specifications or upgrade the database engine version of the primary RDS instance, your database service also becomes unavailable. The unavailability can last for a long period of time. Therefore, if you require high service availability, we recommend that you use the High-availability Edition.
- If an RDS instance runs MySQL 5.7, you can upgrade the RDS instance from the Basic Edition to the High-availability Edition by changing the instance specifications. For more information, see Change the specifications of an ApsaraDB RDS for MySQL instance.
- If your RDS instance runs SQL Server, you can upgrade the RDS instance from the Basic Edition to the High-availability Edition by using the ApsaraDB RDS console. For more information, see .
Create an RDS instance that runs the High-availability Edition
- Can I access the secondary RDS instance?
No, you cannot access a secondary RDS instance. You can access only a primary RDS instance. A secondary RDS instance serves only as a standby and does not allow external access.
- Can I downgrade my RDS instance from the High-availability Edition to the Basic Edition?
No, you cannot downgrade your RDS instance from the High-availability Edition to the Basic Edition. 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.