PolarDB for PostgreSQL (Compatible with Oracle) clusters use compute nodes of dedicated specifications. A compute node of dedicated specifications does not share CPU, memory, storage, and I/O resources with other nodes that are deployed on the same server. This improves the stability and reliability of the compute node.
The following table describes the compute node specifications supported by PolarDB for PostgreSQL (Compatible with Oracle) clusters.
Specifications of compute nodes
Node type | CPU and memory | Maximum storage capacity | Maximum number of connections | PSL4 maximum IOPS | PSL5 maximum IOPS |
polar.o.x4.medium | 2 cores, 8 GB memory | 100 TB | 800 | 8,000 | 16,000 |
polar.o.x8.medium | 2 cores, 16 GB memory | 100 TB | 1,600 | 8,000 | 16,000 |
polar.o.x4.large | 4 cores, 16 GB memory | 100 TB | 1,600 | 32,000 | 64,000 |
polar.o.x8.large | 4 cores, 32 GB memory | 100 TB | 3,200 | 32,000 | 64,000 |
polar.o.x4.xlarge | 8 cores, 32 GB memory | 100 TB | 3,200 | 64,000 | 128,000 |
polar.o.x8.xlarge | 8 cores, 64 GB memory | 100 TB | 3,200 | 80,000 | 160,000 |
polar.o.x4.2xlarge | 16 cores, 64 GB memory | 100 TB | 3,200 | 128,000 | 256,000 |
polar.o.x8.2xlarge | 16 cores, 128 GB memory | 100 TB | 12,800 | 128,000 | 256,000 |
polar.o.x4.4xlarge | 32 cores, 128 GB memory | 100 TB | 12,800 | 128,000 | 256,000 |
polar.o.x8.4xlarge | 32 cores, 256 GB memory | 300 TB | 25,600 | 192,000 | 384,000 |
polar.o.x4.6xlarge | 48 cores, 192 GB memory | 100 TB | 12,800 | 128,000 | 256,000 |
polar.o.x8.6xlarge | 48 Cores, 384 GB memory | 300 TB | 25,600 | 192,000 | 384,000 |
polar.o.x4.8xlarge | 64 cores, 256 GB memory | 300 TB | 25,600 | 192,000 | 384,000 |
polar.o.x8.8xlarge | 64 cores, 512 GB memory | 500 TB | 36,000 | 204,800 | 409,600 |
polar.o.x8.12xlarge | 88 cores, 710 GB memory | 500 TB | 36,000 | 256,000 | 512,000 |
polar.o.x8.15xlarge | 120 cores, 920 GB memory | 500 TB | 36,000 | 256,000 | 512,000 |
Maximum number of connections
When the number of concurrent connections to a PolarDB for PostgreSQL (Compatible with Oracle) cluster exceeds the specified maximum number of connections, subsequent connection attempts time out or fail.
The memory consumption of each connection varies based on the business system. The actual number of connections supported by your cluster may differ from the specified maximum number of connections.
To query the specified maximum number of connections, execute the following statement:
show max_connections;To query the current number of connections, execute the following statement:
select count(1) from pg_stat_activity;We recommend that you monitor your business conditions and cluster status and make sure that the number of connections to the cluster does not exceed the recommended value. You can calculate the recommended value by using the following formula:
LEAST({DBInstanceClassMemory/11MB}, 5000).If your application requires a higher number of connections, we recommend that you use a cluster with larger memory.