Windows Server 2012 and R2: How to check windows deduplication
Connect your server and open roles tab. You can check here!
https://itbrotherss.files.wordpress.com/2018/09/screenshot_1.png
Other way, Disk> and right click deduplication settings. Check here if marked checkbox.
https://itbrotherss.files.wordpress.com/2018/09/screenshot_2.png
and we can check from powershell with this commands.
https://itbrotherss.files.wordpress.com/2018/09/screenshot_3.png
If the backup software we are using uses deduplication, do not activate a double deduplication on the server.