VM Snapshots

Overview

A snapshot saves the state of a virtual machine (VM) at a point in time. You could take a snapshot, for example, before you update critical packages or software that might break a production server. It is also possible to save the state of the VM's memory (RAM). However, you should leave this option off/unchecked except in specific circumstances.

This article describes the processes of creating, naming, rolling back, and deleting snapshots via two interfaces, the UT-VMG Self-Provisioning interface and the vSphere interface. The video demonstration summarizes the processes described in this article.

Notes: Do not save snapshots longer than necessary. Aged snapshots may degrade a VM's I/O performance, as the underlying original virtual disk becomes read-only, while the snapshot "delta" disk tracks all the changes from the underlying. Over time, a snapshot will grow and become slower to update. The UT-VMG team highly recommends a maximum of two snapshots per VM. Snapshots left for longer than 14 days will be automatically removed (changes merged into the VM). VMware's best practices recommend removing snapshots after 3 days.

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The UT-VMG Self-Provisioning Interface

Create a VM Snapshot

• Select the VM you want to snapshot > click the Action menu > select Create Snapshot.

• Name the snapshot or keep the default name (a virtual machine can have multiple snapshots associated with it). You can also add an optional description, e.g. for a maintenance event that encompasses multiple phases (OS patches, application update, change application startup options, etc.).
• Unless specifically needed, you should leave the Memory Snapshot button unchecked.
• Click SUBMIT.
• Refresh the page until the Action menu updates to include Delete Snapshot.

Roll Back a VM to a Snapshot

1. Select the VM > click the Action menu > select Revert to Snapshot.

2. In the window that appears, select the snapshot you want to roll back to.

3. Confirm and click Submit. 
4. Click Submit again to start the rollback. This will shut down the VM if it is powered on, then roll the VM's state back to the state of the snapshot.

Note: After you roll back/forward to or from a snapshot, the VM usually powers back on automatically, but you may need to "Power On" the VM manually. The UT-VMG interface will still show the VM as "Powered On" but it can take approximately 5 minutes before the interface reflects the actual state change.

Delete a VM Snapshot

1. Select the VM > click the Action menu > select Delete Snapshot.
   

2. Click Submit to finish deleting the snapshot.

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The vSphere Interface

Create a VM Snapshot

1. Log into the vSphere Web Client (check https://ut.service-now.com/sp?id=kb_article&number=KB0013467 for vCenter URLs).
2. Search for or navigate to your VM.
3. From the Action menu, choose Take Snapshot.

4. Enter a name and (optional) a description for the snapshot.
5. Uncheck "Snapshot the Virtual machine's memory" in most cases. Reverting to snapshots that include the VM memory can cause problems with some applications. If memory is not included in the snapshot, the machine will be in a crash consistent state if reverting is necessary. 
6. Click Ok. The progress will display in the Recent Tasks pane on the right side.

Roll Back VM to a Snapshot

1. Log into the vSphere Web Client (check https://ut.service-now.com/sp?id=kb_article&number=KB0013467 for vCenter URLs).
2. Search for or navigate to your VM
3. From the Actions menu, choose Manage Snapshots.
4. Select the snapshot from the list and click REVERT.
   

5. Click Yes to confirm > click Close. Progress will be displayed in the Recent Tasks pane on the right of the screen.

Delete a VM Snapshot

1. Log into the vSphere Web Client (check https://ut.service-now.com/sp?id=kb_article&number=KB0013467 for vCenter URLs).
2. Search for or navigate to your VM
3. From the Actions menu, choose Manage Snapshots.
4. Select the snapshot from the list and click DELETE.

5. Click Yes to confirm > click Close. Progress will be displayed in the Recent Tasks pane on the right of the screen.

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Video Demonstration

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