Is One of VMware's Best Features a Really Bad Idea?

Who ever said moving VMs from one physical server to another was a way to improve stability or manage server capacity wisely?

By Kevin Fogarty
Fri, July 25, 2008

CIO — One of the more interesting things about covering the computer business is the number of "Duh" moments involved.

I don't mean the conversations where you're way out of your depth and an enthusiastic savant is walking you through the IT equivalent of quantum physics for kindergarteners, hoping you'll pick up the technology quickly enough to talk about why it's important in the first place.

And not the monologues with those who only think they're savants, misinterpret your suicidal stupor for awestruck reverence and their own need to sell you a bill of goods for evangelical zeal.

If you're curious about or involved with technology at all, you look forward to the former situation as a an opportunity for a guided tour of the future, and dread the latter as evidence that relatives of the tick and tapeworm have successfully evolved into soul-sucking intellectual parasites. Unless you feel a need to pre-pay a karmic debt through suffering, in which case they're all good.

The best kind of "Duh" moment usually comes in the middle of a conversation with someone with impressive expertise on a topic you feel as if you already understand pretty well, until they undermine one of your major assumptions.

Like, say, the idea that being able to move a virtual machine from one physical server to another is a good thing. How could it not be?

Isn't one of virtualization's greatest features the ability to move an application and the VM on which it runs from a balky or overloaded physical server to a better one without having to do more than point and click?

Every data center manager wants or needs the ability to shift VMs around while they're running, preferably without even touching them, by setting up rules that say a VM should move when capacity on its host hits a predefined capacity level. Right?

"In a development or QA environment, sure, that makes a lot of sense. I can't imagine why I'd want to do that in a production environment, though," says Chris Steffen, principal technical architect at Kroll Factual Data, a credit-reporting and financial-information services agency in Loveland, Colo.

"Hot-provisioning is a cool gimmick, but on a scale of one to 10, with 10 being critical, live migration of VMs is about a three," Steffen says. "I don't know what kind of environment other than QA or development, or in a staging environment you'd want to do it, but it's not going to be in any production environment I'm responsible for; it's not going to be any environment dependent on any kind of SLA or performance requirements. The justification for the inherent risk just isn't there."

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