PolarStore Level 4 (PSL4) storage is formally released in PolarDB for PostgreSQL.


PSL4 is a new storage type launched in PolarDB. PSL4 uses the Smart-SSD technology developed by Alibaba to compress and decompress stored data at the physical SSD disk level. This can minimize the storage price of data.

Release date

August 27, 2022


Storage typeChinese mainland regionsRegions outside the Chinese mainland
PSL5USD 0.00077/GB/hourUSD 0.365/GB/monthUSD 0.00085/GB/hourUSD 0.403/GB/month
PSL4USD 0.0005/GB/hourUSD 0.238/GB/monthUSD 0.000552/GB/hourUSD 0.263/GB/month


  • Smart-SSDs use the AliFlash 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.
  • FPGA or ASIC chips are used to compress data. This can reduce the amount of data written to storage and save storage space. High free space can decrease write amplification inherent in standard SSD disks and improve disk performance.
  • Data compression reduces accesses to data stored in physical flash memory and enhances data access performance. When the gains of lower accesses to data exceed the overheads of data compression and decompression, the overall disk performance is boosted.
  • Smart-SSDs are compatible with the access interfaces of standard disks that are transparent to upper-layer applications to avoid complex adaptation of applications.


Cost-effectiveness is prioritized.