PolarDB for PostgreSQL supports two storage types: PolarStore Level 4 (PSL4) and PolarStore Level 5 (PSL5). This topic describes the differences between the two storage types, helping you choose a suitable storage type.
Overview
Storage type | Benefit | Scenario |
PSL5 | PSL5 is the storage type used in historical versions of PolarDB and the default storage type of PolarDB clusters purchased before June 7, 2022. PSL5 provides high performance, reliability, and availability. | Business scenarios that require high performance and reliability and use databases as the core of business systems, such as the finance, e-commerce, and public service sectors, and large and medium-sized Internet services. |
PSL4 | PSL4 is a new storage type available for PolarDB. PSL4 uses the Smart-SSD technology developed by Alibaba Cloud to compress and decompress data at the physical SSD level. This reduces the storage price without compromising SSD performance. | Business scenarios that prioritize cost-effectiveness. |
The storage types of existing clusters cannot be changed. To change the storage type of an existing cluster, we recommend that you purchase a new cluster, configure the storage type that you want to use, and then migrate data from the existing cluster to the new cluster.
Pricing
Storage type | Regions in the Chinese mainland | China (Hong Kong) and regions outside China | |||
Pay-as-you-go | Subscription | Pay-as-you-go | Subscription | ||
PSL5 | Dual-zone (hot standby storage cluster enabled) | USD 0.000748 per GB-hour | USD 0.349 per GB-month | USD 0.000834 per GB-hour | USD 0.389 per GB-month |
Dual-zone (hot standby storage cluster and compute node enabled) | |||||
Single-zone (hot standby storage cluster disabled) | USD 0.000374 per GB-hour | USD 0.175 per GB-month | USD 0.000417 per GB-hour | USD 0.195 per GB-month | |
PSL4 | Dual-zone (hot standby storage cluster enabled) | USD 0.000486 per GB-hour | USD 0.231 per GB-month | USD 0.000542 per GB-hour | USD 0.257 per GB-month |
Dual-zone (hot standby storage cluster and compute node enabled) | |||||
Single-zone (hot standby storage cluster disabled) | USD 0.000243 per GB-hour | USD 0.115 per GB-month | USD 0.000271 per GB-hour | USD 0.129 per GB-month | |
Data reliability
Storage type | Data durability |
PSL5 | 99.99999999% |
PSL4 | 99.9999999% |
Performance metrics
For the same node specifications, PSL4 provides the same maximum I/O bandwidth and maximum capacity as PSL5. However, their maximum IOPS capabilities are different. For more information, see Compute node specifications of PolarDB for PostgreSQL Enterprise Edition.
Performance data
The maximum QPS with the IOBOUND load mode is tested in several scenarios using the following environment: 8 cores and 64 GB memory, dedicated cluster, Enterprise Edition PSL5, PSL4, and Standard Edition PL1 disks, and 900 GB of data. The actual test results are shown in the following figure.
