Data centre virtualisation not all roses

By Michael Morisy
Friday, 05 June, 2009

Virtualisation is coming to a network near you, but what do networking professionals really need to know about data center virtualisation and virtual server networks? With budgets tight all around, network administrators must think long and hard about how virtualisation plays into network planning and how soon they will see a return on investment (ROI) from possible purchases.

It is not even clear that all enterprises will see a net benefit from virtual servers.

"There are cases where you can prove a positive ROI for sure for server virtualisation," said Peter Fetterolf, a partner with networking consultancy Network Strategy Partners. "I'm sure there are also many, many cases where you cannot. It really depends on the situation and the enterprise. With server virtualisation, there are a lot [of] issues that need to be analysed."

Unfortunately, Fetterolf said, many of those issues are hidden network costs that are tough to gauge pre-deployment: How will the move affect staffing requirements, and what will be the cost of added complexity, such as increased downtime?

While there might be fewer physical switches and routers, a virtualisation strategy often means more logical, virtual devices that also have to be managed. But now, many traditional networking tools, such as probes, may not spot problems unless specifically created for a virtual environment.

Just because a networking professional cannot see the problem, in other words, does not mean it's not there and in need of some creative responses.

If these changes are not properly accounted for, the network could possibly even see greater, not reduced, network downtime as networking professionals struggle to get a grip on virtualisation.

Not surprisingly, the vendors that are pushing server virtualisation the hardest, like Cisco, dismiss claims of added complexity.

Jackie Ross, vice president of marketing at Cisco, said products like Cisco's new Nexus 1000V will reduce any complexity associated with server virtualisation. The software-based switch offers role-based user interfaces that align with existing IT roles: Data center professionals, for example, will be presented with a virtual fiber channel, while networking pros will work with virtual Ethernet connections.

By allowing IT professionals to interact with a virtual network in much the same way that they would interact with a physical network, such a product should make supporting server virtualisation similar to what they already do.

"These are areas of expertise that exist," Ross said. "We want to make each specialist more efficient in his area."

There's also less physical infrastructure to manage.

"When you have less equipment, you have less equipment to power, less to cool," Ross said. She also said the number of network adapters needed is cut in half since there are fewer physical devices that need to be connected to the network.

Even if the network of virtual servers doesn't force administrators to reinvent the wheel, life won't necessarily be any simpler just because there are fewer physical boxes to manage.

For example, moving to data center virtualisation almost always decreases the number of physical servers, but the number of virtual storage servers, for example, can more than double, according to IDC analyst Rick Villars.

"There are a lot of things here that are simpler if you look at the overall IT planning process," he said. "But that doesn't mean that you are dramatically decreasing the number of systems you have."

Nor does it mean that the headaches of managing dozens of machines can be handed off to the nearest console.

"Most of what we've seen is that virtualisation in and of itself doesn't affect what you do, just how frequently you have to do management tasks and how you plan future capacity expansion or balance traffic," Villars said. "You're still doing the same things, and that's what a lot of people want to stop and automate."

Fetterolf said he had not heard of clients putting virtualisation projects on hold because of worries about added network complexity, particularly given that virtualisation can be a major money saver. Ross said Cisco's virtualisation tools could dramatically cut both operating expenses and capital expenses, with an ROI of a year to 18 months in many cases.

But whether the savings of a network virtualisation project are worth the trouble will be tough to determine unless all the facets of a deployment are fully mapped out.

"When you go to virtualisation on the server level, you've added complexity to the system. A single physical device running 10 virtual servers is more complex than 10 devices," Fetterolf warned. "You could make a case either way, and it would really depend on the specific situation."

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