How Virtualization Is Revolutionizing Business Data Centers

In an industry that's often disappointed by the Next Big Thing, virtualization is delivering, allowing businesses to reduce the need to pile more and bigger server hardware into strained data centers. Here's how companies are reaping the benefits of virtualization, and avoiding the pitfalls.

VMware, founded in 1998, emerged as the virtualization market leader in 2004, displacing IBM. VMware dominates the field for virtualizing servers based on Intel's X86 architecture, a popular but underutilized resource in most data centers. Placing virtual machines on multicore servers, the latest hardware trend, is one of the few ways to capitalize on the full capabilities of those machines without rewriting applications into parallel systems, a difficult task.

An open source project may offer a compelling price-performance alternative to VMware. Simon Crosby, CTO of XenSource, the parent company of Xen, is a Cambridge University-educated South African with a mop of rebellious reddish-brown hair. He says IT managers should focus more closely on the advantages of the Xen VM engine, which is built on a "paravirtualization" approach. That means, under Xen, the Linux or Windows operating system is aware it's been virtualized and requires the hypervisor to do less work communicating with the server's hardware devices.

As a result, XenSource doesn't need to supply hardware device drivers for each server platform it supports. Many of VMware's 2,400 employees are engaged in producing device drivers for ESX Server, Crosby claims, while XenSource can rely on the drivers provided by Red Hat or Suse Linux, or in the case of Windows, those supplied by Microsoft, letting Xen offer 80% of the functionality of VMware at 20% of the cost. VMware charges $3,750 per ESX Server installation compared with $750 for a XenSource-supported version of Xen.

Microsoft is positioning itself for a major role in the virtualization market. Right now, however, it's a laggard, offering Virtual Server as a VM engine under Windows when both VMware and XenSource have moved to the hypervisor stage. At the FCC, Mashaal has tested Microsoft's Virtual Server against VMware's ESX Server and says Microsoft is at least three years behind.

Less is more, says Shorter, as he eliminates servers

Less is more, says Shorter, as he eliminates servers
Getting Windows into the emerging virtual appliance marketplace may prove difficult. It isn't constructed modularly, like Linux, so things can't be added or subtracted easily, which is what helps configure the operating system to the application. So far, the virtual appliance market has been almost exclusively a Linux play.

Microsoft has enlisted XenSource and Novell for help in bringing Linux virtualization to Windows Longhorn, the server version of Vista. Sometime after Longhorn's release next year, Microsoft will add its still-in-development Viridian hypervisor, which will run Linux as a VM.

If all goes according to plan, in the data center of tomorrow, systems administrators will manipulate virtual appliances, virtualized files, and a mix of virtual machines to allocate and reallocate resources. But it won't happen overnight.

"Virtualization is an evolutionary path," says Mendel Rosenblum, a Stanford University associate professor and co-founder and chief scientist of VMware. Rosenblum did the original work on virtualizing the X86 architecture, and at VMworld he enjoyed guru status. He's also Greene's husband, and echoes her thoughts on the step-by-step nature of virtualization. "You can start with server consolidation, then drop in virtual appliances," he says. "The end result is a radical change."

Radical change without the revolution. It explains virtualization's rapid acceptance--and promising future.

Illustration by Ryan Etter

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