Calculation of Snapshot Space

Snapshots are almost always used by backup products to secure active virtual machines from the outside (not via agent in the guest, but VCB). This is due to the hard drive files of a VM having exclusive read/write access through the VMkernel until a VM snapshot is created. At this point in time, the original hard drive files are readable, and the last Delta file has exclusive write/read access through the VMkernel.

This table illustrates the technical process of a snapshot.

VM snapshot growth