A few days ago, Microsoft pushed the KB5016691 optional update to Windows 11 users, and a little earlier brought a similar KB5016693 update for Windows Server 2022.
Both updates mentioned Server Message Block (SMB) compression improvements in the logs. Recently, Microsoft’s Ned Pyle talked specifically about SMB compression improvements in a blog post.
SMB compression allows system administrators, users, or applications to transform the compression form when transferring files over the Web. This eliminates the need to first compress-send with compression software and then decompress on the target PC. With SMB support, compressed files will consume less network bandwidth and reduce transfer time, at the cost of a slight increase in CPU usage during transfer.
Ned Pyle says that prior to the push of KB5016691 and KB5016693, SMB compression behaved in a strange way, using a default algorithm that first tried to compress the first 500MiB of a file (1MiB is 1024KB), and if the compressible content was above 100MiB, it would compress subsequent content. And anything less than 500MiB will not be compressed, even though the compression is very good, but just not compressed.
In addition, in the previous version, if the algorithm detected a compressible file less than 100MiB during the first 500MiB of the read file, the file would not be compressed even if it was as large as 10GiB.
With the optional update, SMB compression will compress as many files as possible, eliminating the previous algorithm limit.
The improved SMB drawback is that small, low compressibility files will also take up CPU to compress, such as JPG, ZIP, DOCX.
