There could be many things that effect this. Starting with Windows Defender, Windows Firewall, the build version of your dll (to be compatible with Windows 10 current and native .net version), and UAC. Then there are 3rd party programs you may be seeing, Anti-virus, VPN connection, bloatware (many programs and services to enhance or protect-you, filter network traffic, or simply consume unnecessary CPU time). In addition, you could be looking at Network communication protocol on your servers not being as up to date as Windows 10 expects.
For sure you could turn off any of these things to test for 'effect' and narrow down the actual culprit (one or many).
I would try a few basic things. Do 3 direct copies; windows 10 to windows 10, windows 7 to windows 10, and windows 10 to server. Copy a large file (1gb -like inventor install package cab) and catch the maximum copy speed/time. Compare that to your server to windows 10 connection. If this goes full speed both ways, then start looking at your dll to verify what services it uses to process, and test them each. Does the dll require user permissions elevation to run (writing to program files, program data any windows secure folders)? Asking for those permissions inline vs at the beginning changes things. If Defender or other Antivirus is getting in the way, put an exception in it for your program and folders (but don't leave it turned off). Does Server firewall need certain ports opened up?
A clean windows 10 should run faster than windows 7 on the same hardware with all updates in good order. Attempt a bare bones boot (turning off all services that are unnecessary) and test for the service in question. Some that come to mind would be the indexing services that cache data for easy search later, any updating services that may be simultaneously downloading updates while you are copying... As you can see the list can go on and on.
Jamie Johnson : Owner / Sisu Lissom, LLC https://sisulissom.com/
