Using Snapshots to Preserve Virtual Machine StatesA snapshot includes the contents of the virtual machine memory, virtual machine settings, and the state of allthe virtual disks. When you revert to a snapshot, you return the memory, settings, and virtual disks of thevirtual machine to the state they were in when you took the snapshot.You might want to take snapshots in a linear process if you plan to make changes in a virtual machine. Forexample, you can take a snapshot, continue to use the virtual machine from that point, take another snapshotat a later point, and so on. You can revert to the snapshot of a previous known working state of the project ifthe changes do not work as expected.For local virtual machines, you can take more than 100 snapshots for each linear process. For shared and remotevirtual machines, you can take a maximum of 31 snapshots for each linear process.If you are testing software, you might want to save multiple snapshots as branches from a single baseline in aprocess tree. For example, you can take a snapshot before installing different versions of an application to makesure that each installation begins from an identical baseline.Chapter 4 Using Virtual MachinesVMware, Inc. 65
Figure 4-1. Snapshots as Restoration Points in a Process TreeWindows operatingsystembaselineIE baseFirefox baseSP1IE base1You AreHereFirefox base1SP2IE base2Firefox base2Multiple snapshots have a parent-child relationship. The parent snapshot of a virtual machine is the snapshoton which the current state is based. After you take a snapshot, that stored state is the parent snapshot of thevirtual machine. If you revert to an earlier snapshot, the earlier snapshot becomes the parent snapshot of thevirtual machine.In a linear process, each snapshot has one parent and one child, except for the last snapshot, which has nochildren. In a process tree, each snapshot has one parent, one snapshot can have more than one child, andmany snapshots have no children.Using the Snapshot ManagerYou can review all snapshots for a virtual machine and act on them directly in the snapshot manager.You must use the snapshot manager to perform the following tasks.nShow AutoProtect snapshots in the Snapshotmenu.nPrevent an AutoProtect snapshot from being deleted.nRename a snapshot or change its description.nDelete a snapshot.All other snapshot actions are available as menu items in the Snapshotmenu under the VMmenu.When you open the snapshot manager for a virtual machine, the snapshot tree appears. The snapshot treeshows all of the snapshots for the virtual machine and the relationships between the snapshots.The You Are Hereicon in the snapshot tree shows the current state of the virtual machine. The other icons thatappear in the snapshot tree represent AutoProtect snapshots, snapshots of powered-on virtual machines,snapshots of powered-off virtual machines, and snapshots that are used to create linked clones.