Desktop virtualization packages rely on snapshots and virtual drive functionality. The de facto functionality standard here is found in VMware Workstation and VMware Server, but the tools in Sun’s VirtualBox may be setting a new standard. Let’s take a quick look at how snapshots and virtual drives work within Sun xVM VirtualBox.
VirtualBox snapshot technology provides the same basic functionality as the VMware products in that they can be taken while the virtual machine (VM) is running or offline. The snapshots are taken from two different places depending on the state of the VM. For a running VM, the snapshot is taken from the running console as shown in the figure below.
When a VM is powered off, snapshots may be taken in the properties of the VM. This difference is a slight inconvenience, but is an easy learning curve to overcome. Further, if a VM needs to revert to a saved snapshot, this same location is where the VM would be reverted. VirtualBox gives the option to build from the snapshots, so there can be multiple point-in-time restores for a single VM. Snapshots in VirtualBox are kept in the
.VirtualBox\Machines\VMName\Snapshots location by default, and are a collection of .VDI and .SAV files. The figure below shows three point-in-time restores for a single VM:
As with all snapshot restores, you should be sure that you want to restore as the reverting process is authoritative to the VM. Reverting to a VirtualBox snapshot taken while the system is running reverts precisely to that point with the VM running, rather than a powered off state. Overall, the functionality inventory of VirtualBox snapshot functions as advertised and brings another positive view to this exciting virtualization platform.
More information on the VirtualBox 1.6.x product can be found in the online user guide.