Shadow Copy Disk Requirements

how is the initial snap shot of a volume created using Shadow Copy done?
I understand that subsequent versions of a volume created using shadow copy simply creates a copy of only changes to files but i havnt been able to find a black & white description of how the original base line is created.
Im assuming that an entire copy of the volume must be created for there to be any possibility of restoring a file that has been deleted.
This being true, the disk space requirement for shadow copy must be equal to 110% of your present disk usage to allow for a baseline copy and future copies.