Slower SMB Read Performance for large files in 22H2

Slower SMB Read Performance for large files in 22H2

Heya folks, Ned here again. There is a performance regression in 22H2 when copying larger files from a remote computer down to a Windows 11 computer. A large (multi-GB file) might see as much as 40% less throughput over SMB when copying down (reading). Copying that same file to a non-22H2 machine (writing) won’t see this problem.  


For a workaround, use robocopy or xcopy with the /J (unbuffered IO) parameter. For example:


robocopy \\someserver\someshare c:\somefolder somefile.ned /J


That will return your performance to 22H1 throughput. The issue is not actually in SMB code, so I can’t give you an ETA for a permanent fix yet; SMB is just the most likely scenario to be noticed. We’re working with another team to understand this and have them get a permanent fix to you.


I will update this post with more info when I know more. Thanks for your patience.


Ned Pyle


via Microsoft Tech Community

October 3, 2022 at 06:41PM
Ned Pyle