Poor Network Performance on Windows Server 2019 Hyper-V Virtual Machines with Intel 10Gbps X540, X552 and X710 NICs

I migrated my pfSense VM from a Server 2016 to 2019 host and noticed a precipitous drop in WAN transfer speeds.

1. I installed the latest Intel Network Adapter Driver for Windows Server 2019 ¹ for my Intel X552 NIC on my physical Hyper-V host on Server 2019.
2. I continued to notice strange window scaling behaviour, with my WAN speed almost 1/10th of the speed once the VM was migrated to 2019. Migrating the VM back to a 2016 instantly brought performance back up to expected levels.
3. SMB server performance on the 2019 host was also slow. File shares located on this server were sluggish/slow and resulted in unexpectedly low transfer speeds.
4. I issued the following PowerShell commands to restore performance ²:

    #RUN ONLY ON NATIVE2019, HV2019, VM2019
    #Change the TCP-Stack-Settings back to state of Server 2016 
    #Get-NetTCPSetting | ft -AutoSize
    Set-NetTCPSetting -SettingName "InternetCustom" -CongestionProvider CTCP
    Set-NetTCPSetting -SettingName "InternetCustom" -DelayedAckTimeoutMs 50
    Set-NetTCPSetting -SettingName "InternetCustom" -ForceWS Disabled
   
    Set-NetTCPSetting -SettingName "DatacenterCustom" -CongestionProvider DCTCP
    Set-NetTCPSetting -SettingName "DatacenterCustom" -CwndRestart True
    Set-NetTCPSetting -SettingName "DatacenterCustom" -ForceWS Disabled
   
    Set-NetTCPSetting -SettingName "Compat" -ForceWS Disabled
   
    Set-NetTCPSetting -SettingName "Datacenter" -CongestionProvider DCTCP
    Set-NetTCPSetting -SettingName "Datacenter" -CwndRestart True
    Set-NetTCPSetting -SettingName "Datacenter" -ForceWS Disabled
   
    Set-NetTCPSetting -SettingName "Internet" -CongestionProvider CTCP
    Set-NetTCPSetting -SettingName "Internet" -DelayedAckTimeoutMs 50
    Set-NetTCPSetting -SettingName "Internet" -ForceWS Disabled
   
    #RUN ONLY ON NATIVE2019, HV2019, VM2019
    #Disable RSS & RSC on the TCP-Stack 
    #netsh int tcp show global
    netsh int tcp set global RSS=Disabled
    netsh int tcp set global RSC=Disabled
   
    #RUN ONLY ON HV2019
    #Disable Software RSC on all vSwitches
    Get-VMSwitch | Set-VMSwitch -EnableSoftwareRsc $false
       
    #Disable vRSS on all VMs on the host
    Get-VM | Set-VMNetworkAdapter -VrssEnabled $FALSE
   

5. I’d recommend avoiding Intel 10Gbps NICs in the future. X552 and X7xx series have caused a lot of performance problems for me.