Windows 11 22H2 bug affecting file copy speeds over network (fixed)

Windows 11 22H2 can slow down file copying by up to 40 percent due to a kernel bug.

Windows 11 22H2 file copy bug
  • Microsoft confirms a bug causing performance issues copying files on Windows 11 22H2.
  • The bug can slow down file copying by up to 40 percent.
  • The company has resolved the issue and is testing a fix available on build 25267.
  • You can avoid this problem using robocopy or xcopy or staying on version 21H2 a little longer.

UPDATED 12/15/2022: If you recently upgraded to Windows 11 22H2 (2022 Update) and have to copy a large number of files, it’ll probably take a lot more time than using version 21H2. Microsoft has recently acknowledged that the latest version of Windows 11 has performance degradation problems when transferring multi-gigabytes of files to a remote computer.

According to a new post on the Tech Community forums (via Neowin), Ned Pyle, Principal Program Manager at Microsoft, explains that Windows 11 22H2 can slow down transfer speeds up to 40 percent using Server Message Block (SMB) protocol when copying large files over the network.

The post also notes that the problem is not an issue with the SMB code, as the slow throughput performance also appears when copying local files without using SMB.

The company is currently investigating the issue, and there’s no estimated time for a permanent fix, but it’s offering workarounds. If you notice throughput performance issues while copying files, Microsoft recommends using the robocopy or xcopy command tools with the /J option to get around the problem. For example, robocopy \\server\sharepath c:\detinationfolder somefile.iso /J.

Although, for the most part, the Windows 11 2022 Update is off to a good start, the feature update has other known issues regarding copying files and shortcuts, installing updates, and others.

Update December 5, 2022: Microsoft has announced that a preview of the fix is available with the build 25252 in the Dev Channel, and the company plans to roll out the fix for the SMB performance issue once the changes have been validated.

Update December 15, 2022: Another preview of the fix is available with build 25267 in the Dev Channel. The fix is expected to arrive (presumably)