Snapshot Management

Snapshots are NOT backups

A virtual machine snapshot is not a copy so it cannot be treated as a direct backup. A snapshot file is simply a log of changes to the original virtual disk. The virtual machine is running on the most current snapshot, not the original vmdk disk files. To reiterate: snapshots are not copies of the VM's 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 of running with snapshots

• Decreased performance if there are too many delta files in a chain (caused by having too many snapshots).

• Decreased performance if delta files become too large.

• Cannot increase Virtual Disk size while snapshots are active.

• Delta files can grow to the same size as the original base disk file: a virtual machine's provisioned storage size can grow to ( its original size ) multiplied by ( the number of snapshots ).

Requesting a Snapshot

To request a snapshot for your VM, please use one of the following methods:

• Use the VSS Portal - Request Virtual Machine Snapshot

• Use the VSS Command Line Interface 

• Use the ITS Private Cloud RESTful API 

Reverting to a Snapshot

To revert a VM to (or from) a specific snapshot, please use one of the following options:

• Use the VSS Command Line Interface 

• Use the ITS Private Cloud RESTful API

• Send an email to vss(at)eis.utoronto.ca

Deleting a Snapshot

To delete a snapshot for your VM, please use one of the following methods:

• Use the VSS Command Line Interface 

• Use the ITS Private Cloud RESTful API

• Send an email to vss(at)eis.utoronto.ca

Consolidate Disks 

To consolidate VM disks, please use one of the following options:

• Use the VSS Command Line Interface 

• Use the ITS Private Cloud RESTful API

• Send an email to vss(at)eis.utoronto.ca

Recommended Reading

• Understanding virtual machine snapshots in vSphere (VMware KB Article 1015180)

• Best practices for virtual machine snapshots in the VMware environment (VMware KB Article 1025279)

• How to consolidate disk snapshots (VMware KB article 2003638)
   vSphere client: right click on the VM name, go to "Snapshots", choose "Consolidate".
   vSphere Web client: click "Actions" tab, go to "All vCenter Actions", go to "Snapshots", choose "Consolidate".