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Working with snapshots (1009402)

Purpose

This article guides you through understanding and using snapshots in VMware products. It explains what types of snapshots are available in what versions of the products, common uses for snapshots, and operations that are available.

Resolution

Overview

A snapshot:

  • Represents the state of a virtual machine at the time it was taken.
  • Includes the files and memory state of a virtual machine's guest operating system.
  • Includes the settings and configuration of a virtual machine and its virtual hardware.
  • Is stored as a set of files in the same directory as other files that comprise a virtual machine.
  • Should be taken when testing something with unknown or potentially harmful effects.
  • Is not meant to be a method of backup and recovery. If the files containing a virtual machine are lost, its snapshot files are also lost.
  • Negatively impacts the performance of a virtual machine. This is based on how long it has been in place and how much the virtual machine and its guest operating system have changed since the time it was taken. It is not recommended to run production virtual machines on snapshots on a permanent basis.
  • Can take up as much disk space as the virtual machine itself. If multiple snapshots are possible, the amount of disk space used increases with the number of snapshots in place.

Note: Virtual disks which are configured to be independent-persistent cannot use snapshots.

For more information regarding snapshots and VMware ESX, see Understanding virtual machine snapshots in VMware ESX (1015180).

Types

Snapshot Type
Product
Notes
Single
ESX 2.x and earlier
VMware Server
ACE 2.x and higher
Only one snapshot can exist at any given time.
With ACE, the instance must have been created with policies that allow snapshot manipulation. Even if this is disabled, when the virtual machine is created with Workstation it can be set to revert to a snapshot when powered off. If this is done, the virtual machine has a snapshot in place even though it cannot be directly accessed.
Multiple
ESX 3.x and higher
Workstation 5.x and higher

Multiple snapshots can exist at once. Also, refer to the section Snapshot Trees below.
None
ACE 1.x
Player
Snapshots are not supported. However, when the virtual machine is created with Workstation it can be set to revert to a snapshot when powered off. If this is done, the virtual machine has a snapshot in place even though it cannot be directly accessed.

Operations

Snapshot Operation
Effect
TakeThe current state of the virtual machine and its guest operating system is captured.
Revert
The state of the virtual machine and its guest operating system reverts back to what it was when a snapshot was taken. If there are multiple snapshots, the snapshot taken immediately prior to the current state is used.

Warning: All current data is permanently lost.
Delete
The state of the virtual machine is changed to the current state (that is, changes made after taking the snapshot are saved to the parent snapshot disk). In earlier versions of some products the menu option is named Remove.
Delete (Snapshot Manager)
The state of the virtual machine is changed to the current state (that is, changes made after taking the snapshot are saved to the parent snapshot disk). The snapshot chosen to be deleted is available for selection in a graphical display that shows all existing snapshots. This is available only in products that support multiple snapshots.
Go To (Snapshot Manager)
The state of the virtual machine and its current guest operating system switches to the state of that of an arbitrarily chosen snapshot. The snapshot chosen to switch to is available for selection in a graphical display that shows all existing snapshots. This is available only in products that support multiple snapshots.

Snapshot Trees

Snapshot trees are only available in products that support multiple snapshots. A snapshot tree shows all snapshots for a virtual machine and the relationship between snapshots.
This an example of a snapshot tree as seen in VMware Workstation's Snapshot Manager:

Note: The graphical representation of VMware ESX's Snapshot Manager is different but the information displayed is the same.
  • You Are Here represents the current state of the virtual machine and its guest operating system.
  • Windows XP Profession... represents the virtual machine itself and is not a snapshot. You cannot use Go To to switch to this state nor can it be deleted.
  • To Go To one of the existing snapshots but not permanently lose the current state of the virtual machine and its guest operating system:

    1. Take a snapshot.
    2. The new snapshot is shown between Snapshot for Clone of... and You Are Here.
    3. Go To the snapshot you choose. The current state of the virtual machine is lost.
    4. Work on the virtual machine in its previous state.
    5. When finished, use Go To to return the virtual machine to the state saved in step 1.

      Note: Any changes made to the virtual machine in step 4 are lost unless another snapshot is taken.
       
  • If you delete a snapshot you do not affect the current state of the virtual machine or any other snapshot. 
  • Snapshots can be a simple sequential series of virtual machine states. An example of this is just the first row above.
  • To create one or more snapshots outside of a sequential series, Go To a previous snapshot and take a new snapshot. For example, if only the first row in the above existed Go To Test Case 1 Pass and create the new snapshot Test Case 2 Pass.

Tags

create-snapshot consolidate-snapshots delete-snapshots

See Also

Request a Product Feature

To request a new product feature or to provide feedback on a VMware product, please visit the Request a Product Feature page.

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