ApsaraDB RDS is available in four editions: Basic Edition, High-availability Edition, Cluster Edition, and Enterprise Edition. This topic describes High-availability Edition.

High-availability Edition is a widely used edition of ApsaraDB RDS. If you use this edition, your database system consists of a primary RDS instance and a secondary RDS instance. These instances work together in a high-availability architecture. High-availability Edition is suitable for more than 80% of business scenarios, such as Internet, IoT, online retail, logistics, and gaming.

Note
  • The secondary RDS instance runs as a standby for the primary RDS instance and does not allow external access.
  • In extreme circumstances, High-availability Edition may fail 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 Enterprise Edition. For more information, see Enterprise Edition.

Topology

Benefits

  • High availability

    In 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 is inaccessible, your database system fails over to the secondary RDS instance. For more information about data replication modes, see Change the data replication mode of an ApsaraDB RDS for MySQL instance.

    The primary RDS instance and the secondary RDS instance can reside in the same zone or in different zones of the same region.

    Note If the secondary RDS instance is inaccessible, the primary RDS instance performs backups in real time. When a backup is near completion, 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

    High-availability Edition provides a complete suite of features, such as 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 way, you can trace database access behavior and ensure the security of important data.

Limits

For performance purposes, you must deploy the primary RDS instance and the secondary RDS instance in the same region.

Upgrade the RDS edition of an RDS instance to High-availability Edition

If you use Basic Edition, your database system consists of only a primary RDS instance. 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 is 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 is also unavailable for a long period of time. Therefore, if you require high service availability, we recommend that you use High-availability Edition.

You can create an RDS instance that runs High-availability Edition. You can also upgrade the RDS edition of a created RDS instance from Basic Edition to High-availability Edition. The upgrade eliminates the need to migrate data and reclaim the original RDS instance.
Note

Create an RDS instance that runs 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 runs only as a standby and does not allow external access.

  • Can I downgrade the RDS edition of my RDS instance from High-availability Edition to Basic Edition?

    No, you cannot downgrade the RDS edition of your RDS instance from High-availability Edition to Basic Edition. You can create an RDS instance that runs Basic Edition, migrate the data of your original RDS instance to the new RDS instance, and then release your original RDS instance. For more information, see Migrate data between RDS instances.

  • If my RDS instance runs 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 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 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.