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Understanding virtual machines: Part two

Last week, we introduced virtual machines, this week we look at two examples.

Recall some types of VMs run as an application on a host operating system while there are others that do not need a host OS. The VM we look at that needs a host OS is Windows Virtual PC. The other VM, that doesn't need an OS, is VMware's ESXi.

Windows Virtual PC, formerly Microsoft Virtual PC, comes with some versions of Windows 7. It supports the running of other, usually older, Windows OS like XP but it works as well with other operating systems like Linux. The only drawback is users will not find support from Microsoft for non-Windows operating systems. The main use of Microsoft Virtual PC is providing an easy method for Windows 7 users to run older Windows applications, which was a big problem with Vista.

VMware's ESXi is a free program that supports the running of multiple operating systems simultaneously, each self-contained in a virtual space apart from each other. The main use of ESXi, apart from learning virtual machine operation, is running multiple operating systems, typically servers, on a single physical computer.

A number of advantages come from virtual machines. The amount of energy and physical space used by one VM is far less than multiple physical computers and data backup is simplified. One substantial computer VMing multiple servers is individually expensive but overall cheaper than multiple physical servers. Some Internet users fearful of malware are using VMs to access the Web. Any malware contracted is contained within the VM, never the host. They simply delete and recreate the VM if infection is suspected.

The disadvantages of VMs include lower efficiency because of indirect hardware access and if the VM computer faults it immediately affects all the running virtual machines.

Ron Poland is a professor in the Computer Information Systems AAS program at Clinton Community College. Poland is certified in company repair and networking by the Computer Technology Industry Association (CompTIA). He is also a Cisco certified network assistant. Questions may be sent to him via e-mail at ron@ronpoland.com.

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