Microsoft explains the SMB compression changes introduced by Windows Server 2022 KB5016693 and Windows 11 KB5016691 updates
Last week, Microsoft released previews of updates for various versions of Windows before it unleashes the final versions next Patch Tuesday. Included among these was the KB5016691 update for Windows 11 which --although billed primarily as a bug-fixing update -- added new Server Message Block (SMB) compression options.
The same changes were introduced to Windows Server 2022 with the KB5016693 update, and Microsoft has published details of just what the changes mean, as well as explaining how to take advantage of the new options and settings.
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With the release of the update previews, Microsoft did not give a great deal of information about the SMB compression changes. At the time, the company said simply: "New! Compresses a file regardless of its size if you have configured Server Message Block (SMB) Compression".
In the newly published blog post, however, there is a much more detailed explanation of what has been changed and added.
Microsoft Ned Pyle explains:
There was an idiosyncrasy in the initial design that we changed with the release of Windows Server 2022 update KB5016693 (OS Build 20348.946) and Windows 11 update KB5016691. From now on, if you request compression over SMB, we will attempt to compress the file regardless of its size or seeming suitability for compression. It doesn't matter how you request compression - robocopy, share setting, registry values - we will try to compress the file.
Microsoft has also added a new set of Group Policy, PowerShell and registry options to control the legacy behaviors which avoid editing the registry by hand for configuring client compression. More details are available in the blog post.