Using VM snapshots
Last updated
Last updated
A VM snapshot can be used to quickly and easily revert a virtual machine to a previous state.
After taking a snapshot, changes made to the VM are stored in a separate file rather than being immediately committed to the machine's virtual disks. In the event that a change needs to be rolled back, the snapshot can be reverted to immediately return the VMs virtual disks to the exact state they were in when the snapshot was taken.
Notes:
Snapshots consume additional storage and may introduce an impact to VM performance, as such they are not a backup solution, and should only be used for short periods when performing maintenance or making changes that require an option for an easy roll-back.
A VM can only have 1 snapshot running at a time. If a VM is already running a snapshot and another is taken, the first snapshot will be automatically committed to disk before the new one is taken. Once the second snapshot is taken there is no way to revert to the original snapshot.
When a snapshot is removed, all changes made to the VM while the snapshot was running are committed to disk and can no longer be reverted.
In order to take a snapshot, there must be adequate unused storage allocation in the vCloud account. The required storage allocation is equal to the total current size of the VM (ie. if a VM is 200GB in size, 200GB of additional storage must be available for a snapshot to succeed). If a snapshot is attempted without adequate available storage, the snapshot task will fail.
Step 1. Login to the vCloud Director portal
Step 2. Click into the Virtual Datacenter that has the VM you want to snapshot
Step 3. Locate the VM you want to snapshot and click 'Actions'
Step 4. From the drop down menu click on 'Snapshot' > 'Create Snapshot'
Step 5. Choose whether to snapshot memory of the VM
Note: Including memory (RAM) in a snapshot allows a VM to be reverted to it's previous state instantly without requiring a reboot, however, depending on the amount of RAM assigned to the VM, the snapshot may take considerably longer to perform as the contents of RAM need to be written to disk. If a reboot of the VM is acceptable in the event a snapshot needs to be reverted, it is generally recommended to leave this option disabled
Step 6. Click 'CREATE' to take the snapshot and wait for the task to complete
Step 1. To remove a snapshot after successful maintenance or changes have been completed, locate the VM you want to remove the snapshot for and select 'Actions'
Step 2. From the drop down menu click on 'Snapshot' > 'Remove Snapshot'
Step 3. Click 'Remove'
Step 1. To revert a snapshot, locate the VM you want to revert the snapshot for and select 'Actions'
Step 2. From the drop down menu click on 'Snapshot' > 'Revert to Snapshot'
Step 3. Click 'REVERT'
If memory was included in the snapshot, the VM will immediately return to its previous state with no downtime.
If memory was not included in the snapshot, the VM will turn off and roll back to its previous state. It can then be powered on again manually.
