Introducing Heterogeneous DR Instances

GaussDB(for MySQL) supports heterogeneous DR instances to ensure high availability. If your DB instance is unavailable due to unknown community bugs, misoperations or AZ faults, the heterogeneous DR instance can take over the services.

The DR instance creation, maintenance, and switchover are all completed by Huawei Cloud and you do not need to do anything.

The free trial of heterogeneous DR instances has ended on January 1, 2024.

Figure 1 Heterogeneous DR instance

Constraints

Heterogeneous DR instances cannot be created in the scenarios listed in the following table.

**Table 1** Constraints
Scenario	Reason
Binlog is not enabled.	Binlogs are used to synchronize data between the GaussDB(for MySQL) instance and DR instance.
binlog_format is not set to ROW.	The DR link may be disconnected.
There are triggers.	Data may be inconsistent between the GaussDB(for MySQL) instance and the DR instance.
There are events.	Data may be inconsistent between the GaussDB(for MySQL) instance and the DR instance.
Database names, table names, field names, or indexes contain special characters.	The DR link may be disconnected.
The data volume exceeds 4 TB.	The capacity of the DR instance has an upper limit.
The database access is restricted by rules in the security group.	The DR instance cannot connect to the GaussDB(for MySQL) instance to synchronize data.
The GaussDB(for MySQL) instance is frozen.	The DR instance cannot be created.
There are no sufficient IP addresses in the VPC subnet.	The DR instance and GaussDB(for MySQL) instance need to use IP addresses in the same subnet.
There are tables without primary keys or indexes and a large number of operations.	The DR link may be disconnected.
Cascade operations are performed on tables with foreign keys.	Data may be inconsistent between the GaussDB(for MySQL) instance and the DR instance.