Why does the speed not rise above 3.5Gbit / s from the declared 10Gbit / s?

Question

Computer networks

written on 03.07.2017 10:43 Info • Private • Edit • Reply • Notify moderator • IP
Good day. I ask for advice. 2 identical Intel S5520UR servers are used.
The task was to raise 10Gbit / s
As a result, the speed does not rise above 3.5-4Gbit / s
Windows Server 2008R2 OS is installed
Mellanox MNPA19-XTR ConnectX-2 EN
network card ASUS PEB-10G / 57811-1S network card
Completed 1. Installing
drivers with 10G support
https://downloadcenter.intel.com/ru/download/18388...
2.Updating BIOS
3.The cards are fixed in the PCI-e x8 slot riser
Tests.
Testing was carried out on 2 desktop PCs. With the installation of boards in the x16 slot. Everything is fine, the speed showed 8.5-9gbit / s. Windows 10 OS
What else does he need?
I'm considering an OS upgrade.

Answer 1

According to the specification, the S5520UR supports the pci-e 2.0 standard, which gives ~ 4 Gbit / s per line. Most likely your riser divides x8 one line per extension slot, that's your 4Gb/s.

Answer 2

Have you tried running tests without a riser?
I don't know where... Apparently, in the network card driver parameters, all offloads that are available should be enabled.