A global database network (GDN) consists of multiple PolarDB for MySQL clusters that are deployed in multiple regions within a country. This topic describes GDNs.
- Active geo-redundancy
If you deploy applications in multiple regions but deploy databases only in the primary region, applications that are not deployed in the primary region must communicate with the databases that may be located in a geographically distant region. This results in high latency and poor performance. GDN replicates data across regions at low latencies and provides cross-region read/write splitting. GDN allows applications to read data from a database local to the region. This allows databases to be accessed within 2 seconds.
- Geo-disaster recoveryGDN supports geo-disaster recovery regardless of whether your applications are deployed in the same region. If a fault occurs in the region where the primary cluster is deployed, you need only to manually switch your service over to a secondary cluster.Note A typical failover can be completed in 10 minutes. In most cases, failovers can be completed within 5 minutes. During the failover, services may be interrupted for up to 60 seconds. We recommend that you perform the switchover during off-peak hours and make sure that your applications are configured to automatically reconnect to the database service.
- Zero code modification for deployment: If an application is deployed in one region, you can deploy it in multiple regions without the need to modify code. For more information, see Cross-region deployment.
- Cross-region read/write splitting: GDN clusters can handle both read and write requests. Read requests are sent to the cluster in the same region while write requests are forwarded to the primary cluster. For more information, see Cross-region read/write splitting.
- Flexible configuration: The primary and secondary clusters can be configured separately. The configuration of a cluster includes cluster specifications, whitelists, and parameter values. For more information, see Create a GDN.
- Low-latency data synchronization across regions. Physical replication is performed over multiple channels, which allows data to be replicated across all nodes at a latency of less than 2 seconds even under heavy loads. For more information, see Low-latency synchronization across regions.
You are not charged for the traffic that is generated during cross-region data transmission within a GDN. You are charged only for the use of PolarDB for MySQL clusters in the GDN. For more information about the pricing rules of PolarDB for MySQL clusters, see Billable items.
Supported regions and clusters
- Regions: GDN is available in more than 10 regions, including regions inside the Chinese mainland, the China (Hong Kong) region, and regions outside China. For more information, see Region mappings between the primary and secondary clusters.
- A cluster in a GDN must use one of the following versions:
- A PolarDB for MySQL 8.0.2 cluster
- A PolarDB for MySQL 8.0.1 cluster
- A PolarDB for MySQL 5.7 cluster whose revision version is 188.8.131.52.13 or later
- A PolarDB for MySQL 5.6 cluster whose revision version is 184.108.40.206.27 or later
- The primary cluster and secondary clusters must have the same database engine version, which can be MySQL 8.0, MySQL 5.7, or MySQL 5.6.
Region mappings between the primary and secondary clusters
GDNs cannot communicate across countries. You can add only secondary clusters that are in the same country as the primary cluster. The following table lists the region mappings between the primary and secondary clusters in a GDN.
|Region of primary cluster||Region of secondary cluster|
|All regions in Chinese mainland||Any region in Chinese mainland. |
For example, if the primary cluster is in the China (Hangzhou) region, secondary clusters can be in the China (Hangzhou) region or other regions in Chinese mainland.
|China (Hong Kong)||China (Hong Kong)|
|Japan (Tokyo)||Japan (Tokyo)|
|South Korea (Seoul)||South Korea (Seoul)|
|Australia (Sydney)||Australia (Sydney)|
|Malaysia (Kuala Lumpur)||Malaysia (Kuala Lumpur)|
|Indonesia (Jakarta)||Indonesia (Jakarta)|
|Philippines (Manila)||Philippines (Manila)|
|India (Mumbai)||India (Mumbai)|
|Germany (Frankfurt)||Germany (Frankfurt)|
|UK (London)||UK (London)|
|US (Silicon Valley)||US (Silicon Valley) and US (Virginia)|
|US (Virginia)||US (Silicon Valley) and US (Virginia)|
|Philippines (Manila)||Philippines (Manila)|
|Thailand (Bangkok)||Thailand (Bangkok)|
Get started with GDNs
For more information, see Create and release a GDN.