Windows 11 2022 Update may slow file transfer by up to 40%

WindowsThe new Windows 11 2022 (22H2) update is this year’s big update to Microsoft’s operating system, which brought important news in terms of graphics, productivity and integration with Android. As often happens in these cases, however, not everything seems to have gone well and the company itself has confirmed a bug that slows the transfer of large files (over 1GB) by up to 40%. The problem was described by Microsoft’s Ned Pyle in a community forum post, in which he explains that

a large file (several GB) may see up to 40% slower speed on Server Message Block (SMB) when copying (reading). Copy the same file to a machine [non mise à niveau vers] 22H2 (write) will not encounter this problem

Pyle notes that the problem isn’t in the SMB code, but that’s the most likely scenario where you’ll notice the problem. This means that the slowdown is not necessarily seen only in the network share, but it can also be seen in the transfer of local (large) files. According to Pyle, however, it is possible to work around the problem and describes how, using robocopy or xcopy with the /J (unbuffered IO) parameter:

robocopy \\a_server\a_folder c:\a_folder a_file.ned /J

Using this command to copy a file will restore the transfer speeds that existed before the Windows 11 22H2 update.