DR Overview

To prevent service unavailability caused by regional faults, DRS provides disaster recovery to ensure service continuity. You can easily implement disaster recovery between on-premises and cloud, without the need to invest a lot in infrastructure in advance.

The disaster recovery architectures, such as two-site three-data-center and two-site four-data center, are supported. A primary/standby switchover can be implemented by promoting a standby node or demoting a primary node in the disaster recovery scenario.

Figure 1 Real-time DR switchover

Supported Database Types

The following table lists the database types supported by DRS.

**Table 1** DR schemes
Service Database	DR Database	Documentation
On-premises MySQL databases MySQL databases on an ECS MySQL databases on other clouds RDS for MySQL	RDS for MySQL	From MySQL to MySQL (Single-Active DR) From MySQL to MySQL (Dual-Active DR)
	GaussDB(for MySQL)	From MySQL to GaussDB(for MySQL) (Single-Active DR)
DDM	DDM	From DDM to DDM (Single-Active DR)
GaussDB(for MySQL)	GaussDB(for MySQL)	From GaussDB(for MySQL) to GaussDB(for MySQL) (Single-Active DR) From GaussDB(for MySQL) to GaussDB(for MySQL) (Dual-Active DR)

Basic Principles of Real-Time Disaster Recovery

DRS uses the real-time replication technology to implement disaster recovery for two databases. The underlying technical principles are the same as those of real-time migration. The difference is that real-time DR supports forward synchronization and backward synchronization. In addition, disaster recovery is performed on the instance-level, which means that databases and tables cannot be selected.

Next topic: DR Scenarios