PolarDB for PostgreSQL(Compatible with Oracle) provides two storage types: PolarStore Level 4 (PSL4) and PolarStore Level 5 (PSL5). This topic compares the two storage types to assist your selection.
Overview
| Storage type | Benefit | Scenario |
|---|---|---|
| PSL5 | This is the storage type supported by historical versions of PolarDB and the default storage type for PolarDB clusters purchased before June 7, 2022. It delivers higher performance, reliability and availability. | Databases are the key component of business systems that require high reliability, such as finance, e-commerce, public service sectors, and medium- or large-scale Internet services. |
| PSL4 | As a new storage type for PolarDB, PSL4 uses the Smart-SSD technology developed by Alibaba Cloud to compress and decompress data at the physical SSD disk level. This can minimize the storage price of data while keep a high disk performance. | Cost-effectiveness is prioritized. |
Note The storage type of existing clusters cannot be changed to Standard Edition. To use Standard Edition, we recommend that you purchase a new cluster, set the storage type to Standard Edition, and then migrate data to the new cluster.
Pricing
| Storage type | Regions in the Chinese mainland | Regions outside the Chinese mainland | ||
|---|---|---|---|---|
| Pay-as-you-go | Subscription | Pay-as-you-go | Subscription | |
| PSL5 | USD 0.00077/GB/hour | USD 0.365/GB/month | USD 0.00085/GB/hour | USD 0.403/GB/month |
| PSL4 | USD 0.0005/GB/hour | USD 0.238/GB/month | USD 0.000552/GB/hour | USD 0.263/GB/month |
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 of PSL5 and the same maximum capacity as PSL5. For more information, see Specifications of compute nodes.
Performance
In particular scenarios, PSL4 offers slightly lower performance because of its decompression process. In most cases, PSL4 delivers almost the same performance as PSL5.