Snapshots are not backups

A snapshot file is only a change log of the original virtual disk. Therefore, do not rely on it as a direct backup process. The virtual machine is running on the most current snapshot, not the original vmdk disk files.
Snapshots are not complete copies of the original vmdk disk files. Taking a snapshot does not create a complete copy of the original vmdk disk file, rather it only copies the delta disks.

Side Effects

• An excessive number of delta files in a chain (caused by an excessive number of snapshots) or large delta files may cause decreased virtual machine and host performance. 
• Not able to increase size of Virtual Disk.
• Delta files can grow to the same size as the original base disk file, which is why the provisioned storage size of a virtual machine increases by an amount up to the original size of the virtual machine multiplied by the number of snapshots on the virtual machine.

Recommended Reading

• Understanding virtual machine snapshots in VMware ESXi and ESX (VMware KB Article 1015180)
• Best practices for virtual machine snapshots in the VMware environment (VMware KB Article 1025279)

Requesting a Snapshot

You can request a snapshot for your VM by filling out the following Snapshot Request form.

Reverting to Snapshot

To revert to Virtual Machine snapshot could be done by sending an email to vss(at)eis.utoronto.ca.