PolarDB:Purchase a cluster

Background information

• The number of read-only nodes supported by a centralized PolarDB for PostgreSQL cluster depends on the Database Edition. An Enterprise Edition cluster can have one primary node and up to 15 read-only nodes. A Standard Edition cluster can have one primary node and up to 7 read-only nodes. To ensure high availability, make sure that a cluster has at least one read-only node in addition to the primary node. The primary node and read-only nodes operate in active-active failover mode, which enables automatic switchover in the event of a primary node failure. If the primary node fails, a read-only node can automatically take over as the new primary node, ensuring uninterrupted database availability.

  Note

  PolarDB delivers optimal performance only when it communicates with other Alibaba Cloud products over the internal network. Therefore, we recommend that you use PolarDB along with Elastic Compute Service (ECS) and deploy the PolarDB cluster on the same VPC as the ECS instance. Otherwise, PolarDB cannot deliver optimal performance.

• A PolarDB for PostgreSQL Distributed Edition cluster is built on a PolarDB for PostgreSQL Centralized Edition cluster. It uses a two-layer architecture of compute nodes (CNs) and data nodes (DNs) to achieve distributed scalability and separate computing and storage resources. It supports all existing capabilities of the PolarDB for PostgreSQL Centralized Edition cluster and also fully meets the diverse performance and reliability requirements of enterprise-level business.