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Gotcha No. 2: Getting the Right Staff Experience is a Challenge

IDG Research Services, a sister unit of InfoWorld, surveyed 464 participants late last year about their virtualization experience. The biggest challenge? Forty-four percent of respondents said inadequate skills and training was the most difficult hurdle, followed by software licensing issues, performance and scalability challenges, and complexity.

So don't expect the IT staff to have all the answers to virtualization from the get-go. It'll take at least a month to gain an accurate understanding of current server workloads, given weekly and monthly spikes, before deciding which servers can be virtualized. In small companies with only a handful of IT folks, you may need to hire -- surprise! -- a pricey consultant to conduct capacity planning.

A small company also may not have the necessary SAN expertise or, for instance, capability to mesh Cisco switches and VMware's complex virtual networking stack. "Virtualization draws together so many different aspects of networking, server configuration, and storage configuration that it requires a well-seasoned jack-of-all-trades to implement successfully in a small environment," Prigge wrote in a "virtual" case study for the Test Center that’s chock full of insight about challenges ranging from pricing and products to technical and skills requirements.

Larger companies don't have it easier, either. Getting a lot of people in disparate teams -- server, storage, business continuity, security -- on the same page is a feat, especially since they traditionally don't talk to each other very much. All of them, though, need to be educated about virtualization. If there's a problem with an application, for instance, an administrator must know where virtual machines exist throughout the server farm so that he doesn't reboot a server and unwittingly take down all the virtual machines on it.

Gotcha No. 3: Performance Boosts Aren't Always What They're Cracked Up to Be

Despite the hard work, virtualization adopters may feel a sting of disappointment. Many will have embraced server virtualization with grand expectations, only to see performance fall short. Burton Group's Wolf points the finger at vendors: "For me, the way VMware advertises performance benchmarks is completely inaccurate."

The vendor publicity materials' virtual machine benchmarks involve running a single virtual machine on a single physical host. But a typical production environment is conservatively eight to 12 virtual machines per physical host. "This paints an overly optimistic picture of performance," Wolf adds. "They also tend to gloss over things like over-allocation of CPU cores" that can tax the hypervisor's CPU scheduler and lower performance.