and PolarDB for PostgreSQL offer two storage types: PSL4 and PSL5. This topic compares these two storage types to help you select the right option for your workloads.
Storage types
|
Storage type |
Features |
Use cases |
|
PSL5 (PolarStore Level 5) |
PSL5 is the storage type used in earlier versions of PolarDB and was the default for clusters purchased before June 7, 2022. It delivers high performance and greater reliability and availability. |
Business-critical applications that require high performance and reliability, such as finance, e-commerce, government services, and large to medium-sized internet businesses. |
|
PSL4 (PolarStore Level 4) |
This new storage type from PolarDB uses Alibaba Cloud's proprietary Smart-SSD technology to compress and decompress data at the physical SSD level. This technology lowers storage costs with a manageable impact on performance. |
Cost-sensitive applications that prioritize a high price-performance ratio. |
A cluster's storage type generally cannot be changed. However, an in-place upgrade from PSL4 to PSL5 is supported. For other changes, such as downgrading, you must create a new cluster and migrate your data.
Storage pricing
|
Storage type |
Chinese mainland |
China (Hong Kong) and other regions |
|||
|
Pay-as-you-go |
Subscription |
Pay-as-you-go |
Subscription |
||
|
PSL5 |
Dual-zone (hot standby storage enabled) |
USD 0.000748/GB/hour |
USD 0.349/GB/month |
USD 0.000834/GB/hour |
USD 0.389/GB/month |
|
Dual-zone (with hot standby storage and a standby compute node) |
|||||
|
Single-zone (hot standby storage disabled) |
USD 0.000374/GB/hour |
USD 0.175/GB/month |
USD 0.000417/GB/hour |
USD 0.195/GB/month |
|
|
PSL4 |
Dual-zone (hot standby storage enabled) |
USD 0.000486/GB/hour |
USD 0.231/GB/month |
USD 0.000542/GB/hour |
USD 0.257/GB/month |
|
Dual-zone (with hot standby storage and a standby compute node) |
|||||
|
Single-zone (hot standby storage disabled) |
USD 0.000243/GB/hour |
USD 0.115/GB/month |
USD 0.000271/GB/hour |
USD 0.129/GB/month |
|
Data reliability
|
Storage type |
Data durability |
|
PSL5 |
99.99999999% |
|
PSL4 |
99.9999999% |
Upgrading the storage type
If PSL4 storage no longer meets your business needs, you can manually upgrade the storage type to PSL5 in the PolarDB console.
Prerequisites
Your cluster must meet the following conditions:
-
Billing method: subscription or pay-as-you-go
NoteServerless clusters do not support storage type upgrades.
-
Edition: Enterprise Edition
-
Series: Cluster Edition
-
Storage type: PSL4
PolarDB for PostgreSQL (Distributed) does not support storage type upgrades.
Procedure
-
After you upgrade the storage type, the system recalculates the fees based on your cluster's storage billing method. For more information, see Billing for configuration changes.
-
The storage type cannot be downgraded from PSL5 to PSL4. Evaluate your requirements carefully before you perform the upgrade.
-
Log on to the PolarDB console. In the left-side navigation pane, click Clusters, select the cluster's region, and then click the cluster ID.
-
On the cluster details page, find the Distributed Storage section and click Storage Upgrade.
Performance metrics
For the same compute node specifications, PSL4 and PSL5 offer the same maximum storage capacity and I/O bandwidth, but differ in maximum IOPS. For more information, see and Compute node specifications for Enterprise Edition.
Performance comparison
The following comparison is based on QPS tests in I/O-bound scenarios on a dedicated cluster with 8 cores and 64 GB of memory. The backend storage configurations tested were Enterprise Edition with PSL5, Enterprise Edition with PSL4, and Standard Edition with PL1 cloud disks. The data volume was approximately 900 GB.
