PolarDB for MySQL provides two storage types: PolarStore Level 4 (PSL4) and PolarStore Level 5 (PSL5). This topic describes the differences between the two storage types to help you select a storage type suitable for your business.
Overview
Storage type | Feature | 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 in-house 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 type of existing clusters cannot be changed. To change the storage type of an existing cluster, we recommend that you purchase a new cluster, specify the storage type that you want to use, and then migrate data from the existing cluster to the new cluster by using an external migration tool such as Data Transmission Service (DTS) or the major version upgrade feature of PolarDB. For information about major version upgrades, see Major version upgrades.
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 deployment (hot standby storage cluster enabled) | USD 0.000770 per GB-hour | USD 0.3650 per GB-month | USD 0.000850 per GB-hour | USD 0.4030 per GB-month |
PSL 5 | Dual-zone deployment (hot standby storage cluster and hot standby compute cluster enabled) | ||||
PSL5 | Three-zone deployment (hot standby storage cluster and logger node enabled) | ||||
PSL5 | Single-zone deployment (hot standby storage cluster disabled) | USD 0.000385 per GB-hour | USD 0.1825 per GB-month | USD 0.000425 per GB-hour | USD 0.2015 per GB-month |
PSL4 | Dual-zone deployment (hot standby storage cluster enabled) | USD 0.000500 per GB-hour | USD 0.2380 per GB-month | USD 0.000552 per GB-hour | USD 0.2630 per GB-month |
PSL4 | Dual-zone deployment (hot standby storage cluster and hot standby compute cluster enabled) | ||||
PSL4 | Three-zone deployment (hot standby storage cluster and logger node enabled) | ||||
PSL4 | Single-zone deployment (hot standby storage cluster disabled) | USD 0.000250 per GB-hour | USD 0.1190 per GB-month | USD 0.000276 per GB-hour | USD 0.1315 per GB-month |
Four CPU cores are allocated for the compression of each TB of data in PSL4. The costs associated with CPU cores are included in the storage fees.
Data reliability
Storage type | Data durability |
PSL5 | 99.99999999% |
PSL4 | 99.9999999% |
Performance metrics
For the same compute node specifications, the cluster has the same maximum storage capacity and I/O bandwidth upper limit but different IOPS upper limits when the PSL4 or PSL5 storage type is used. For more information, see Compute node specifications of PolarDB for MySQL Enterprise Edition clusters.
Performance comparison
An IOBound performance test is conducted to measure the maximum queries per second (QPS) that a cluster of dedicated specifications that has 8 cores and 32 GB of memory can handle when the PSL5, PSL4, or PL1 Enterprise SSD (ESSD) storage is used. The size of the test data is approximately 800 GB to 1 TB. The following figure shows the actual test result.
