Why is the write speed through the HBA Adaptec 2100 lower than through the built-in SATA controller?

Question

RAID

There is a Gigabyte S451-Z30 (rev. A00) platform, a storage server built on EPYC. Actually not under a storage, but not an essence. A SAS Adaptec HBA 2100-16i was plugged into it and connected to the backplane. For Samsung SATA SSD PM883 test. A simple Crystal Disk Mark is used as a test (yes, I know that there are many other options, just a quick one, under Windows). Other than these PM883s, there is no load. SAS 12g, SATA 6g. The drives themselves are 6g.
This case has the option of connecting two sata drives directly to the sata controller on the motherboard and 36 drives to the HBA.
When connected to SATA, I get a write speed of 520 MB / s.
When connected to SAS, I get a write speed of 370 mb / s.
Reading speed is the same.
I'm trying to figure out what could be the reason. There would be a MiniHD SAS - SATA cable, I would check the influence of the Backplane, but so far there is no such thing. I turn on Writeback disks in the SAS controller, it does not affect at all.

Answer 1

This is the maximum that the disk is capable of.