Server consolidation isn't the only reason you might want to use virtualization software. In fact, some IT managers run just a single virtual machine (VM) on their VMware virtualization hosts, putting them at a 1:1 consolidation ratio.
For Melbourne IT, a hosting provider in Melbourne, Australia, virtualization represents "a hybrid" between the two predominant hosting models: shared infrastructure and dedicated infrastructure, said Glenn Gore, chief infrastructure architect.
By running applications in a virtual machine on shared hardware, customers get the logical isolation of dedicated hardware, plus a lot of management benefits, Gore said.
"What customers really love [about virtualization] is functionality like snapshotting and rollback. Anyone who's ever worked on a Web site knows that updates don't always work out the way you planned," Gore said.
But not all of Melbourne IT's customers are ready for shared infrastructure. "They say to us, 'We really like all that [management] but we don't want to share.'" Melbourne IT compromises and starts those users off on their own dedicated ESX box. "It allows them to take a small step and hopefully eventually transition to a shared model," Gore said.
The transition to a shared model comes quickly enough, Gore said, since the dedicated ESX server is quite expensive -- especially if you want to use any of VMware's high-availability features. "If you want to use VMotion, all of a sudden you're at a 1:2 ratio, and they say to themselves, 'You know, I don't really need that.'"
"As a sales tool, it's very interesting, but [the customer] is only interested in it until they realize they don't need it," Gore said.
However, there is another case where Melbourne IT will run a single VM per ESX host: when it needs to provide capacity on demand and rapidly scale resources, say, to respond to a one-time phenomenon like a ticketing event.
"Customers have very different usage profiles, and [virtualization] allows us to manage their peak loads," Gore said.
Renewed faith in old hardware
Electronics for Imaging Inc. (EFI), a printing technology development firm in Foster City, Calif., uses virtualization internally to respond to shifts in IT usage. While most of EFI's production applications run on a VMware ESX server farm, the firm also uses VMware's free VMware Server to run an application from its test and development sandbox, said Dave Swan, senior manager of server operations at EFI.
"It's a question of resource management," Swan said. "It gives us the flexibility to boot up a server wherever we want, and it gives us some basic fault tolerance, too."
Running the apps within virtual machines also gives the application owners more faith in aged hardware. "If you run an application on a server that's not brand new, they might feel a sense of risk," Swan said. But since the applications are all stored on a storage area network, "the machine could blow up and die and I could still boot the server up again in five minutes."
Tony Iams, senior analyst at Ideas International Inc. in Rye Brook, N.Y., said he isn't surprised to hear users are running a single VM per host and can think of other reasons they might want to do this: clustering, for example.
"Once a workload is virtual, it doesn't care what kind of hardware it runs on, and the process of bringing it back up on a backup server becomes much easier than it would with clustering," Iams said. Of course, this depends on how demanding the application is, but generally speaking, "users would rather see reduced performance rather than no performance."
One high-performance application IT managers often want to virtualize is Citrix, Iams said. Even though it is very resource intensive, "Citrix runs better if you can restart it on a regular basis," and virtualizing it enables IT managers to easily relaunch it in a pristine environment, he said.
Users tend to naturally stumble on these use cases as their understanding of virtualization matures, Iams said. "I call it the light-bulb effect. You start using virtualization for its really clear economic benefit, consolidation; but then the light bulb goes off, and you say, 'I'm going to virtualize everything!' Once your workloads are virtual, you find your life gets a lot easier."
Let us know what you think about the story; email: Alex Barrett, News Director.