This topic provides answers to some frequently asked questions about the regions and zones of ApsaraDB RDS.
Introduction to regions and zones
A region is a physical data center. After an RDS instance is created, you cannot change its region.
Zones in a region are physical areas with independent power supplies and network facilities. The network latency between instances that reside in the same zone is lower than the network latency between instances that reside in different zones. After an RDS instance is created, you can migrate the instance across zones within the same region.
The following figure shows the relationships between regions and zones.
Can an ECS instance and an ApsaraDB RDS instance that reside in different regions or within different Alibaba Cloud accounts communicate with each other? Am I charged for traffic that is consumed to establish the connections between the instances?
Internet-based connection: You can use the public endpoint of the RDS instance to establish a cross-region or cross-account Internet-based connection to the RDS instance. You are not charged for the inbound and outbound Internet traffic generated on the RDS instance.
Internal network-based connection: If the ECS instance and the RDS instance reside in different regions or within different Alibaba Cloud accounts, you cannot connect the instances over an internal network. VPCs are isolated from each other. However, you can use VPC peering connections or a Cloud Enterprise Network (CEN) instance to connect two different VPCs. This way, the ECS instance can connect to the RDS instance across regions or Alibaba Cloud accounts.
VPC peering connection: enables communication between VPCs across regions or Alibaba Cloud accounts at low costs. However, a VPC peering connection is relatively complex to configure. This method is suitable for simple scenarios in which a small number of VPCs need to be connected.
CEN instance: enables communication between VPCs across regions or Alibaba Cloud accounts at high costs. However, a CEN instance is simple to configure. This method is suitable for complex scenarios in which a large number of VPCs need to be connected.
Can instances in different zones of the same region communicate over an internal network?
Yes, instances in different zones of the same region can communicate over an internal network by using internal endpoints. For more information, see View and change the internal and public endpoints and ports.
Conditions for connections over an internal network
If you want to connect an Elastic Compute Service (ECS) instance to the RDS instance over an internal network, the following conditions must be met:
The ECS instance and the RDS instance are created within the same Alibaba Cloud account and use the same network type.
If the ECS instance and the RDS instance both reside in virtual private clouds (VPCs), the instances must reside in the same VPC.
The private IP address of the ECS instance is added to an IP address whitelist of the RDS instance. For more information, see Configure a whitelist.
Can I change the region of my RDS instance?
No, you cannot change the region of your RDS instance after the RDS instance is created. To change the region of your RDS instance, you can create an RDS instance in the destination region and zone, use Data Transmission Service (DTS) to migrate the data from the original RDS instance to the new RDS instance, confirm that your workloads run as expected, and then release the original RDS instance.
Can I change the zone of my RDS instance?
Yes, you can change the zone of your RDS instance. However, zones in the same region do not have significant differences. You do not need to change the zone of your RDS instance. If you want to change the zone of your RDS instance due to specific reasons, follow the instructions provided in Migrate an ApsaraDB RDS for MySQL instance across zones.
Which deployment method is recommended: single-zone deployment or multi-zone deployment?
Zones in the same region are independent physical areas that are accessible to each another over an internal network. If a zone is faulty, other zones are not affected. If your application requires high disaster recovery capabilities, we recommend that you use the multi-zone deployment method.
For more information, see Create an ApsaraDB RDS for MySQL instance.