X99/C610 motherboard's all SATA port total speed only reach 1.2GB/s write with 1.6GB/s read

hackserver · ‎12-28-2020

I have been entangling this issue for a few days and searching online didn't find any explainsion. I use one CPU E5 2678 v3 on the Huananzhi X99-AD3 motherboard. I connected ten disks. When I test the speed for all the 10 SATA ports, the speed is quite slow. It can't reach DMI 2.0's maxium 2GB/s.

The test result is on Window, the total write speed is around 1.1GB/s and read speed is 1.6GB/s.

While on linux, the total write speed is around 1.2GB/s and read speed is 1.6GB/s.

This is Windows write test using cygwin dd, total speed is around 1.1GB/s

This is Windows read test using cygwin dd, total speed is around 1.6GB/s

This is write test using fio on linux, total speed is around 1.2GB/s

This is read test using dd on linux, total speed is around 1.6GB/s

What's the cause of the speed limit? CPU? motherboard? or PCH chip's ablity?
I don't see anyone else mentioned this issue on internet. Do other X99/C610 motherboard users have the same issue?

n_scott_pearson · ‎12-28-2020

If there is anything limiting speed, it is the bottleneck at the DMI bus. You need to remember that the DMI bus is used for a *lot* more things that just SATA - there's PCIe, USB, GFX steering, SPI, I2C, SMBus, LPC (SIO/EC), HDA (Audio), ME, LAN, WiFi (including CNVi), etc.

...S