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 supported by historical versions of PolarDB and the default storage type for PolarDB clusters purchased before June 7, 2022. PSL5 delivers higher 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. |
You cannot change the storage type of existing clusters. 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 | Hot standby storage cluster enabled | Region in the Chinese mainland | Region outside the Chinese mainland | ||
Pay-as-you-go | Subscription | Pay-as-you-go | Subscription | ||
PSL5 | Yes | USD 0.00077 per GB-hour | USD 0.365 per GB-month | USD 0.00085 per GB-hour | USD 0.403 per GB-month |
No | USD 0.000385 per GB-hour | USD 0.1825 per GB-hour | USD 0.000425 per GB-hour | USD 0.2015 per GB-hour | |
PSL4 | Yes | USD 0.0005 per GB-hour | USD 0.238 per GB-month | USD 0.000552 per GB-hour | USD 0.263 per GB-month |
No | USD 0.00025 per GB-hour | USD 0.119 per GB-hour | USD 0.000276 per GB-hour | USD 0.1315 per GB-hour | |
Data reliability
Storage type | Data durability |
PSL5 | 99.99999999% |
PSL4 | 99.9999999% |
Service level agreement
Storage type | Cluster Edition | Single Node Edition |
PSL5 | 99.99% | 99.95% |
PSL4 | 99.96% | 99.9% |
Maximum IOPS and capacity
For the same node specifications, PSL4 provides half the maximum IOPS and the same maximum capacity as PSL5. For more information, see Compute node specifications of PolarDB for PostgreSQL Enterprise Edition.
Performance
In specific scenarios, the decompression process may lead to a slight decrease in the performance of PSL4. In most cases, PSL4 delivers almost the same performance as PSL5.