Ops Manager backup process Few questions on ops-manager backup process


While backup ops manager creates a head db which is copy of the monogdb deployment 
I want to know the reason behind this. Why create another copy and increase space consumed for backup 
Ops manager takes snapshot of the head db which got created where Backup Daemon is running
What is the type of snapshot?
How ops manager maintains consistency in snapshots for whole cluster?
Whole process is explained here

Backup is created "elsewhere" (than originating data; of course) and that backup is kept "up-to-date". Time to time snapshots (moments in time) is created (and stored) from that data. In the "side" system keeps copy of opLog too, so it is possible to "roll-forward" from snapshot to specific moment in time (between snapshots).