Constraints

Updated on 2025-01-09 GMT+08:00

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GaussDB provides the cross-region disaster recovery (DR) capability to improve your data security. If a disaster occurs in the primary data center, the DR data center takes over services quickly. The cross-region DR is suitable for data centers with a distance greater than 200 km.

The differences between cross-cloud DR and regular on-cloud DR are as follows:

Cross-cloud DR also supports cross-region DR, and you can create a remote DR relationship on the web UI.

Constraints

Constraints on DR relationship establishment:

Currently, a primary instance can only establish a DR relationship with one DR instance. If you want to re-establish a new DR relationship, you must stop the DR relationship between the primary and original DR instances and then select an available instance to be the DR instance.
To establish a DR relationship for distributed instances, the number of shards of the primary instance must be the same as that of the DR instance.
The instances for which a DR relationship is established must use the same OS. DR relationships cannot be established between instances running different OSs, for example, they run on EulerOS and HCE separately.

Constraints during DR relationship establishment:

The DR instance is only used to synchronize data of the primary instance. It cannot read or write data.
The DR instance does not support full backup or differential backup.
Storage of the primary and DR instances cannot be scaled up.
For the primary instance, if the instance is forcibly started when a majority of AZs are faulty, data cannot be synchronized to the DR instance. In this case, you need to disconnect the DR relationship.

If a minority of nodes for the DR instance are faulty, the DR instance still works properly.
If a majority of nodes for the DR instance are faulty, the DR instance cannot be promoted to primary.
When you restore the primary instance to a new instance, the DR user account cannot be automatically deleted. You need to delete the account manually.
The DR instance in a DR relationship does not support adding replicas. After the DR instance is promoted to primary, replicas in the instance can be added.
The resource types (virtualization types) of the primary and DR instances must be the same.
It is recommended that the specifications of the DR instance be the same as those of the primary instance. Smaller specifications of the DR instance will slow down Xlog replay on the DR instance.
Before setting up cross-cloud DR, you need to delegate the DR operation permissions to a system user and connect the two instances properly.
- No action is required if the two instances are in the same VPC.
- If the two instances are deployed in different VPCs, create a VPC peering connection on the Virtual Private Cloud > VPC Peering Connections page of the VPC Endpoint console and configure routes between subnets.
- In cross-cloud scenarios, create a Direct Connect connection.
- Ensure that the security group allows IPv4 inbound traffic from port 12016.
Compatibility constraints:
- In the cross-cloud DR scenario, the peer DR instance name is not displayed in the DR relationship list.
If the pre-verification for a cross-cloud DR operation fails, you can deliver the same operation again on the page after the fault is rectified.