Open source virtualization hypervisor VirtualBox has reached version 3.1, which adds the ability to migrate a live virtual machine session between physical hosts.
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Whether you prefer Linux, Windows, or Mac OS X, you can probably get almost everything you need done with your chosen OS. However, sometimes a task demands an OS that you are not currently using. That's where virtualization programs like Sun Microsystem's VirtualBox 3.0 come in.