Computerworld - Editor's Note: On page 5, this story should have said that the licensing implications aren't clear about the fact that SWsoft virtualized environments don't require a separate instance of the OS. Two points needed to have been made: First, it doesn't matter whether you're using a full OS in every virtual environment or not; it counts as a license for Windows Server. Second, whether you'll pay for that extra license depends on whether you have a Standard Edition, Enterprise Edition or Datacenter Edition license of Windows Server. This story was corrected on Monday, April 2, around 9:55 a.m.
The last "gotchas" installment talked about correctly configuring virtual machines and having the right supporting cast of hardware resources associated with them. But other problems can crop up, too, especially as virtual server adoption builds.
Too much, too quickly
Once virtualization takes hold, it can grow rapidly in many directions and become difficult to manage -- a phenomenon that Matt Dattilo, vice president and CIO at PerkinElmer Inc. in Waltham, Mass., calls "VM creep."
"You have servers here, servers there, but there's no overall management or function in place. No one is keeping track of what is going on," says Bruno Janssens, senior architect of infrastructure architectural services at The Hartford in Hartford, Conn.
As the number of virtual machines climbs from dozens to hundreds, or thousands, tracking what you have becomes challenging. "It's easy to lose track of what's out there in the virtual world," because there are no physical machines to see or serial numbers to record, says David Rossi, managing partner at Sapien LLC, an application service provider in Morristown, N.J., that runs its operations on virtual servers. "The cataloging and administration of that is one of the gotchas,'" he says.
To help resolve that problem, Sapien developed specific process controls and tools to manage its virtual server population.
It's tough enough to track servers that are virtual. Live migration and dynamic workload-balancing tools that continuously move virtual machines between hosts can add to the confusion and run afoul of change management policies. "If you have strict change management procedures in-house, you have to fine-tune" the dynamic resource scheduler, says George Scangas, lead IT infrastructure analyst at Welch's in Concord, Mass.
Virtual machines are essentially image files, and those need to be tracked and managed just like any other server image. As virtual servers become more prevalent, IT organizations need to have a change management database for quickly reproducing virtual server images, says IDC analyst John Humphreys.
A consistent library of virtual machine images can also improve efficiency. "If you're repeating things or constantly developing new images and replacing them as opposed to fixing them in the virtual world, then you're not quite adopting the concept behind virtualization," says Richard Cardona, principal engineer at Surgient Inc., a vendor of virtualized application development and test lab services based in Austin. "Customers with less frequent updates are working smarter," he says.
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