Virtualization means creating a virtual, rather than actual, version of a computing environment. Virtualization is useful for consolidation because one physical server can host several virtual versions of an operating system or application.
Virtualization is a good option for IT shops with several servers that are running applications that do not use up much of the capacity in the box, according to virtualization expert and author David Marshall, co-author of Advanced Server Virtualization: VMware and Microsoft platforms in the virtual data center.
"You may have a group of servers way underutilized. Those are good candidates to be consolidated through virtualization," said Marshall.
Virtualization techniques tackle sprawl
Virtualization technology takes advantage of techniques such as virtual machines, partitions and resource management tools to run different workloads simultaneously on larger servers.
For example, a virtualized server may use software to emulate multiple servers on a single hardware platform so only one physical host is needed.
But the software is more than just about cutting down on the number of box servers in an IT shop said analyst Tom Bittman of Gartner Inc., a Stamford, Conn.-based research firm. Although
"Virtualization is not just about consolidation. It's moving to a different model to using my computing resources, "said Bittman. "I think of computer resources as a pool. I want to manage holistically, not one box at a time."
Virtualization is catching on quickly. Gartner estimates between 80% and 90% of its customers are using some kind of server virtualization software now. The firm predicts that 40% to 50% of servers will be running virtual machines in three years.
There are some drawbacks to the technology, according to virtualization expert Chris Wolfe, co-author of Virtualization: from the desktop to the enterprise. Many administrators have unrealistic ideas for the number of systems they want to virtualize on one server because they are not considering the hardware limitations, Wolfe said.
"The truth is you have to start with the current running server and look at its CPU resource allocation and its memory allocation," he said. "You have to look at your current resources and work backward based on that."
Although virtualization technology may reduce server sprawl in a data center, it can still present significant management challenges.
"I think one of the misconceptions is that if you take 10 servers and consolidate on one box that you will only have one system to manage. The reality is you have 11 managed systems," Wolfe said.
Blades as an alternative
Blade servers are another popular choice for consolidation, but they work more appropriately in data centers with several servers that are operating at or near capacity. A blade server is a chassis housing multiple slim boxes, known as server blades. Each blade is also a server itself, hosting an application or operating system. The slimness of the blade servers cuts down significantly on space because they are much smaller than the traditional rack servers currently used in most server rooms.
Consolidating with blades is simply a physical consolidation and a reduction of server size. Blades are good for shops that are ready to spend the money to update their hardware, Marshall said. Blades in the data center are also an attractive option for IT managers who are more comfortable with something they can touch, he added.
"While upgrading to blade servers is different than migrating from one rack server to another, migrating to new hardware is typically an easier pill to swallow than moving to whole new methodology like virtualization," said Marshall.
Blades are still far off from replacing traditional rack servers completely, but they are gaining market share quickly. Research from IDC in Framingham, Mass., predicts that 25% of servers on the market will be blades by 2009. However, blades are not without their drawbacks. Most blades on the market now generate a lot of heat and create power challenges for IT managers.
A recent survey by TheInfoPro (TIP) Inc., a New York research firm, asked 133 server professionals about their experience with blades and found that most thought they did not provide heating and cooling advantages.
However, TIP Chief Research Officer Bob Gill said blade vendors are realizing that excess power is a problem in terms of energy efficiency, and there is an initiative among them to create blades that are more energy-efficient.
Although blades and virtualization serve different needs, each technology is starting to compete with each other in the server-consolidation market, Marshall said.
"There is an intersection where these two meet and can be combined to solve other unique problems," he said. "But, with regard to consolidation, they certainly step on each other's toes."
There is room for a peaceful co-existence, however. TIP's Gill added that virtualized blades could alleviate some problems with power efficiency and consolidation.
Ultimately, blades and virtualization are technologies that will be used together in the data center of future as more administrators tighten up their space by virtualizing several systems on slim blade servers, said Marshall.