Running multiple OSes at the same time used to be a pipe dream. In the mid '90s, Mac users tethered to Quark Express and other Mac-exclusive desktop publishing applications dreamed of being able to use Windows-exclusive apps, though without recourse. Some tried to bridge the gap by emulating hardware, but the results were extremely slow and proved all but the most basic applications unusable. That all changed a few years ago when Apple announced the unthinkable: the company was switching from the IBM G5 architecture which had done it so proud for so long, and instead moving to Intel-based X86 machines. With the switch, users could freely install Windows as another partition and turn their Mac into the ultimate Windows computer.

That still hadn't eliminated the dream though; users wanted to be able to run Windows applications while still using their Mac OS, without needing to reboot. Enter virtualization, a term which means the ability to run two operating systems simultaneously. Rather than emulation, which requires a software engine to pretend to be other hardware, virtualization simply siphons off some system resources to devote to a guest operating system.

What about users who'd like to go the other way and use Windows with multiple OSes? While there's no virtualization solution that we've found to run Mac OS under Windows (let us know in the comments if you've found one!), we have found multiple solutions to test out Linux without having to restart your machine. Read on as we break down all these scenarios and explain the basics behind virtualization.

Why virtualize?

The biggest reason users would want to virtualize is so that they would be able to use applications side by side without the need to restart. Some cases are obviously more optimal than others. For example, Mac users who'd like to use Chrome as their web browser but don't want to wait for Google to develop a Mac version could use a Mac virtualization solution to run Chrome alongside any other Mac applications. Likewise, users — be they Windows or Mac aficionados — who like to run web servers or other software that works best on Linux without having to give up their regular environment might find some appeal in virtualizing a Linux environment.

Virtualization's other big feature is portability. Since the environment is packed together in a single file, a virtualized environment can be backed up by simply making a copy of the file. That ease of backup means software can be installed at will, and if something breaks, a user can go back to a previous copy without skipping a beat. Users can also create "portable" virtualized environments, which have applications bundled together and can be used on multiple machines.

 

How does it work?

Virtualization takes some of the spare resources not being used by a host operating system and distributes them to the guest operating system. In modern machines, that typically means a user could devote one processing core to a primary OS, and another processing core to a secondary OS. Since the processing cores operate independently from each other, the guest OS will seem fairly responsive once the system has loaded fully, and the host OS won't notice that much of a performance hit in general purpose computing. (Web browsing, word processing, etc.)

High performance computing tasks such as video editing and heavy photo editing are still extremely difficult to do while using a virtualized environment. Most modern high performance applications are multi-threaded, meaning they're built to expect multiple processors and can take advantage of multiple cores. Since one core is essentially devoted to the guest OS, performance will slow from normal levels.

Users looking to run high performance applications, including games, should skip virtualization and instead have a dedicated OS install. Fortunately for Mac users, these "bootcamp" installs can also be run as virtual OSes, as well as stand-alone primary OSes; we'll have more on that in a second.

How do I do it?

To make the jump to virtualization, there are a variety of options. Chief among them are several commercial software options that do an excellent job.

Mac users

Mac users looking to virtualize have two main competing options: VMWare Fusion and Parallels Desktop. Both solutions work in an extremely similar manner, allowing the user to install a virtual operating system and run applications inside of it. While we'd love to declare a definitive winner in the VMWare vs Parallels battle, the real bottom line is both software applications are going to do similar things at similar price points. Both are priced at $80 and do the same job. They also both offer free trials, so if you're not sure about picking one over another, give them both a try.

Mac users can expect to install any OS that is supported by X86, including most distributions of Linux and of course Windows. Both offer a feature that allows Windows applications to work seamlessly alongside Mac applications in their own windows without having to see the Windows desktop or Start Menu; VMware calls it "unity" and Parallels refers to the same feature as "coherence." 

Windows users

While we'd love it if there were a solution for Windows users to run Mac OS, currently no vendor supports living dangerously and violating Apple's EULA. That being said, there are still a number of resources for Windows users looking to give Linux a spin via virtualization.

For a free virtualized installation of Linux, we'd try CoLinux. Not exactly the most simple way to virtualize Linux, as the installation requires text file editing and the like, but it's a simple way to save some cash and run Linux at the same time as Windows.

On the other hand, users looking to virtualize with a bit more ease can try Parallels Workstation. Priced at $50, users can install the software on either Linux to virtualize Windows, or Windows to virtualize Linux. Either way, you can give an OS a spin without having to destroy any current data. VMWare also offers a Workstation option, though it's much more pricey at $150.

Linux LiveCDs

If all you're looking to do is give Linux a spin without losing any data, we'd recommend giving the preponderance of Linux LiveCDs a try. Simply download the image, burn it with your favorite image burning program, and boot from the CD. You'll then be able to try Linux without having to install a thing. The process is painless and doesn't change any of your hard drive data, unless you ask it to.

You should be on your road to virtualizing now. If you've got any questions, leave them as comments on this post. Happy virtualizing!

[Images: Header image by Daniel Morris Story images: Flickr user Lodev. Used courtesy of Creative Commons.]