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 widely used 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, such as the Internet, Internet of Things (IoT), online retail, logistics, and gaming.

Note In extreme circumstances, the High-availability Edition may not be able to prevent data loss. If you require a data security level of 100% and a recovery point objective (RPO) of 0, we recommend that you use the Enterprise Edition. For more information, see Enterprise Edition.

Topology

Benefits

High availability

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. For more information, see Data replication modes.

You can deploy the primary and secondary RDS instances in the same zone or in different zones of the same region.

Note If the secondary RDS instance becomes faulty, the primary RDS instance performs backups in real time. When a backup is about to be completed, a FLUSH TABLE WITH READ LOCK (FTWRL) statement is executed. This triggers a global lock that is held for up to 5 seconds. Before the global lock is released, you can only read data from the primary RDS instance.

Comprehensive functionality

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.

Limits

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 unexpectedly exits, your database service becomes unavailable for a long period of time. If you change the specifications or upgrade the database engine version of the primary RDS instance, your database service also becomes unavailable for a long period of time. Therefore, if you require high service availability, we recommend that you use the High-availability Edition.

You can create an RDS instance that is designed to run the High-availability Edition. Alternatively, you can upgrade a created RDS instance from the Basic Edition to the High-availability Edition. After the upgrade is complete, the new RDS instance carries over the lifecycle of the original RDS instance. This eliminates the need to migrate data or reclaim the original RDS instance.
Note

Create an RDS instance that runs the High-availability Edition

FAQ

  • Can I access a 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 support 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.

  • If my RDS instance runs the High-availability Edition, how do I change the data replication mode of the instance?

    For more information, see Change the data replication mode of an ApsaraDB RDS for MySQL instance.

  • When I use the High-availability Edition, does the data replication mode degrade to the asynchronous mode if the secondary RDS instance cannot process data as fast as the primary RDS instance?

    Yes, when you use the High-availability Edition, the data replication mode degrades to the asynchronous mode if the secondary RDS instance cannot process data as fast as the primary RDS instance. For more information, see Data replication modes.