Windows Tip Sheet

Ride the Virtual Time Machine

Explore and exploit a bevy of great new features in VMware Workstation 5.0 to roll back OS changes and even create virtual machines off different system "snapshots."

If you’re not familiar with virtual computing (products like VMware Workstation or Microsoft Virtual PC), it’s time to crawl out from beneath that rock you’ve been hiding under. In particular, you should be giving a good hard look at VMware Workstation 5.0. VMware and Virtual PC (which became a Microsoft product last year) have always leapfrogged one another in features; VMware’s new version, however, is a pretty big leap forward.

Of special interest to busy Windows admins is the new progressive snapshot feature. Basically, you can take a “snapshot” of your virtual machine at any time, and then revert back to that snapshot whenever you like. It’s kind of like System Restore, only it’s a complete, point-in-time snapshot of the entire OS. So you can install Windows, take a snapshot, do all kinds of testing, and then roll back to that pristine state at any time you like.

What’s better, though, is the ability to build new virtual machines off of those snapshots (a capability Virtual PC offers, in a less-intuitive fashion, through differencing drives). Here’s how it works: You get your virtual machine to whatever point you like (say, Windows installed and fully up-to-date on patches). You shut the virtual machine down and take a snapshot. That snapshot can then form the basis for any number of other virtual machines, each of which exists independently from the others. Need to test a new app? Just create a new virtual machine based on your freshly installed Windows snapshot. You’ll save all the time of installing Windows and get that same, fresh state to work with. Of course, once virtual machines start using a snapshot as a basis, you can’t modify that snapshot. You couldn’t, for example, open up the snapshot and apply a service pack; doing so would invalidate any virtual machine that was based on the snapshot. But this ability does save space: I can have a dozen “freshly installed” Windows XP virtual machines that only take up the space of one, because they’re all using a single, underlying snapshot.

VMware Workstation 5 also has memory-sharing, which essentially means that two WinXP virtual machines, each allocated with 256MB of memory, won’t necessarily use 512MB of real RAM; they can share memory to a degree.

Virtual computing has always been valuable for testing and evaluating software, and features like these snapshots and memory sharing make the virtual computing software even more useful and convenient.

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About the Author

Don Jones is a multiple-year recipient of Microsoft’s MVP Award, and is an Author/Evangelist for video training company Pluralsight. Don is also a co-founder and President of PowerShell.org, a community dedicated to Microsoft’s Windows PowerShell technology. Don has more than two decades of experience in the IT industry, and specializes in the Microsoft business technology platform. He’s the author of more than 50 technology books, an accomplished IT journalist, and a sought-after speaker and instructor at conferences worldwide. Reach Don on Twitter at @concentratedDon, or on Facebook at Facebook.com/ConcentratedDon.

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