I've seen and found similar post online and her but so far no one with an answer.
Windows Server Backup extremely slow while 'compacting
the virtual hard disk(s)'
Compacting virtual hard disks
Running a Windows 2016 Server that has the hyper v role that I backup using the Windows Backup to backup the server to a local attached USB disk.
When I firstly create the backup job it takes quite some time because it needs to copy all the data, which is understandable. After that the incremental is done within a hour backing up 3 TB of data and 6 VMs, which is a great result.
Then after a while the backup disk is filling up and it will take for ever to finish a backup. Every day it will start to do a full and compacting the virtual hard which will take almost the whole day.
