Windows 10: WIN11 KB5036980 breaks SMB Multichannel

As title says, this update breaks SMB Multichannel, i have few PCs with dual gigabit NIC and they all copied files from server at speeds over 200mb/s, after you install KB5036980 it copies only over single NIC around 120mb/s maxUninstalling the KB fixes the issues on all affected computers.

:)

 

Cannot get SMB Multichannel to work (Win 8.1 <-> 10)

Thank you for the advice, I created a new thread there:

https://social.technet.microsoft.co...-to-work-win-81-10?forum=win10itpronetworking

 

Win11 2H22 SMB Multichannel copy speed slow

According to the release note, Windows 11 22H2 has a known issue which will cause the SMB multichannel copying speed limited under 1Gbps:

September 30, 2022—KB5017389 (OS Build 22621.608) Preview - Microsoft Support

But the release note only mentioned as "You are more likely to experience this issue copying files to Windows 11, version 22H2 from a network share via Server Message Block (SMB)", which meant the speed of copying files from Windows 11 to a SMB server (uploading) would not be affected.

Some other users reported that the copying speed from a 3x1Gbps NICs PC to a SMB server could be kept at full speed:

SMB copy limited to 700mbit after 22H2 update - Microsoft Community

But in my case, the file copying speed from a 3x1Gbps NICs PC to SMB server has also been limited:





The upload speed of each NIC has been limited under 270Mbps and in total of 810Mbps.

On the same PC, if there are only 2 NICs installed, the copying speed will be as expected (2Gbps).

So is this problem also caused by the known issue introduced by 22H2, or it's a new issue? Or it is caused by the wrong configuration on my PC?

BTW, the workaround provided in the release note did not work at all, the speed would still be limited with xcopy or robocopy /J command.

 

Event ID: 30822 Failed to establish an SMB multichannel network connection.

Something here is probably what you're looking for however: SMB multichannel troubleshooting - Windows Server