Very Slow Network Copy Performance in Windows
When attempting to copy a large file (several gigabytes) from one Windows system to another, the copy operation may be very slow. In addition, the Networking tab in Task Manager shows the file copy operation proceeding very quickly for a short while, then pausing, then continuing. There is not a continous flow of slow data transfer, but quick bursts. This can happen across Windows versions, older and newer, whether they are communicating at SMB1 or SMB2.
This may happen if the target folder uses compression. Revert the folder to uncompressed.
Compression is no longer a very useful feature in Windows' NTFS file system. The files which typically consume the most disk space (pictures, video, music) do not compress much anyway. Thus the processing and file system overhead required to achieve compression is not comensurate with the space savings to be achieved.