I use this command to backup vms:
wbadmin start backup -backuptarget:<shared folder> -hyperv:<vm name> -quiet
I thought that WSB was compressing or otherwise reducing the size of the backups because the backup of vm with a 2 Tb data drive that has 1.5 Tb free takes up only 554 Gb (includes a 80 Gb system volume)
However, another vm with a 1.5 Tb data drive that has 730 Gb free requires 1.6 Tb disk space for its backup.
Can someone help me understand what factors control the size of the backup and how they might be operating in this case.?