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PolarDB:How do I choose between PSL4 and PSL5?

Last Updated:May 09, 2024

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.

Note

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.