Virtual Machine Snapshot

A virtual machine snapshot is an image of a virtual machine's disk at a specific point in time. It's a read-only copy that can be used to create a new virtual machine or restore a VM to a previous state. Essentially, it's a backup mechanism and a templating tool rolled into one.

You can create two types of VM snapshots in Private Cloud Director.

Type 1 - VM Ephemeral Disk Snapshot

This type of snapshot is created when you take a snapshot of a virtual machine that is using an ephemeral disk as it's root disk. A new image gets created in the Image Library that captures the state of the VM's disk, including its data and configuration, at the moment the snapshot is taken.

Note that if a VM is created with ephemeral root disk, and then mounts one or more block storage volumes as data volumes, taking a snapshot of such a VM will only create a snapshot of it's root disk. The data volumes will not be snapshotted or tracked as part of the VM snapshot. To fully recreate such VM using a snapshot in the future, you need to first snapshot the VM and then separately take a volume snapshot of the data volumes. Then during VM restore or recreation time, you can create a new VM first using the VM snapshot, and then mount the volumes data volumes on this VM using the volume snapshots you created above.

Important

Taking a snapshot of a VM with ephemeral root disk will only snapshot the root disk. Any volumes attached to the VM will NOT be included in the snapshot.

Type 2 - VM Volume Snapshot

This type of snapshot is created when you snapshot a virtual machine that is using a volume for it's root disk. When you snapshot such a virtual machine:

• The VM's root disk volume is snapshotted as a bootable volume snapshot

• If the VM has any other volumes mounted, those volumes are also snapshotted.

• A VM Volume Snapshot file is create that is essentially a metadata file that tracks the boot volume snapshot and the data volume snapshots, along with other required information.

When a new VM gets created using this snapshot, it will be booted using the bootable volume snapshot created from the step above, and the remaining volume snapshots will be mounted as disks on the VM.

Snapshot Creation

You can take a snapshot of virtual machines in running or powered off state. In the UI, select the snapshot action for the VM to take the snapshot.

Snapshot Storage and Viewing

All virtual machine snapshots are always stored in the Image catalog. For the snapshot of volume based root disk vms, the snapshot metadata file that stores the information about volume snapshots - is also stored in the image catalog.

You can view VM snapshots in the image catalog by looking at the images view in the UI. All VMs snapshots will have the image_type=snapshot property set. You can view this property in the properties column.