One of a system administrator's many responsibilities is to ensure that newly published system patches, including full service packs, work as intended -- and if they don't, to find out how they fail to interact with an existing setup. So what's the best way to test such patches in a controlled environment?
The generic recommendation is to reserve a standalone Windows machine to be used as a guinea pig and to set it up to resemble a standard workstation as closely as possible. However, given how tight IT budgets are nowadays and the fact that some shops simply don't have the physical space for a test machine, this isn't always a practical suggestion.
One alternative is virtual computing. Programs like Microsoft Virtual PC and VMware make it possible to emulate a PC's entire operation (hard drive, operating system, network, etc.) on another PC's desktop. With this type of tool, an administrator can create a virtual test machine with the same software loaded onto the average user's computer. It also makes testing substantially easier: If the administrator wants to back up the test system before determining how a particular patch behaves, all he has to do is copy a file instead of re-image an entire computer.
Often, the emulated machine can run at approximately 75% of its host's speed, and speed isn't typically a primary concern when testing for compatibility and proper patch behavior.
Note that if you use a specific hardware configuration that cannot be emulated in a Virtual PC (for instance, a biometric identification device), this type of tool may be less useful, depending on which one you use. VMware supports the near-transparent emulation of most USB hardware, while Virtual PC does not.
About the author: Serdar Yegulalp offers his expertise in Windows NT, Windows 2000, Windows 2003 and Windows XP as publisher of the Windows Power Users Newsletter.
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This was first published in May 2005