Virtualization: Just Because You CAN Doesn't Mean You Should...

By Gail Dutton
published: Monday, June 16 2008

Just because you can do something doesn't mean you should. The adage stands the test of time, whether the issue is eating that second piece of cake, skydiving or virtualizing the enterprise.  None of these things are inherently dangerous, but they do beg one to consider whether the risks are worth the reward.

The risks of virtualization lack the rather dire consequences of a chute not opening, but there are there and they must be adequately considered in light of the potential benefits. Generally speaking, viability of virtualization decreases as hardware usage and numbers of users increase. Poor candidates for virtualization, therefore, tend to be enterprise-wide servers (including file, web and application servers), SQL and Oracle hosts, and high-usage database hosts. Messaging services and production servers are borderline.

The Gartner Group's rule of thumb calls for a six month payback from server virtualization efforts. Good virtualization candidates thus include underutilized hardware, and applications with relatively few users, such as database hosts with small numbers of users, under-utilized Web servers, development servers, legacy NT servers and low-usage application servers. The Gartner Group advises focusing on older, smaller packaged applications when determining what should be virtualized. If applications are effectively using established hardware, any gains from virtualization would be negligible.

University of Utah Healthcare (UUH), the university's healthcare center, took that message to heart when it began its virtualization process a few years ago. With an average CPU utilization of 7 percent, server virtualization was a good candidate for virtualization and became the logical first step. "There was good opportunity to consolidate," recalls Bryan Peterson, principal systems engineer. Peterson learned that the conservative 4:1 server ratio initially estimated could be bumped to a 10:1 ratio, increasing payback without harming performance.

"We didn't look so much at memory virtualization," he continues. Instead, UUH consolidated memory with a ballooning approach that engaged an enterprise-wide virtual distributed resource scheduling plan to monitor ESX server usage. The plan ensures that the host machine always has sufficient memory before letting guest machines use any extra memory. Virtual Motion software allows virtual machines to be moved among physical machines without any downtime, in a way that is transparent to users. Consequently, Peterson says, "you don't have to worry about maxing out memory." The strategy, he continues, is to see how applications perform and move them if necessary.

In the process, Peterson discovered that "Java is not a good virtualization candidate. We had to rewrite a few applications two or three times -primarily those with heavy Java components. Certain applications are virtual machine (VM) aware and adapt to the way time slices are handled. Java can't cope with that," he says.

Licensing

Licensing agreements also will help determine what should or should not be virtualized.  Application vendors don't all support virtualization, as UUH learned. And, those that do support virtualization tend to have different pricing strategies. Understanding these policies can affect what you virtualize.

For example, when third party logistics provider Transplace was virtualizing its operations in 2007, what began as a straightforward need for more space became a complete hardware refresh and a move to a co-location facility. When CTO Vince Biddlecombe took a hard look at the overall system, he quickly saw that licensing concerns had a profound impact on subsequent costs and thus affected the choice of hardware.

The decision, for Transplace, was between more servers (a Sun system) or bigger servers (an IBM system). In the end, application licensing agreements resolved the issue. At the time, Oracle licenses were based upon CPU usage. "Since I pay per processor," it made sense to choose a powerful system that minimized the CPUs running. Thus, "I could run five or six copies of a database on one server and use fewer servers and save money," Biddlecomb says. He chose the IBM system, using two CPUs for production and one for disaster recovery.

HP's encounter with licensing issues centered around verification. When virtualization was quite new, "We ran eight CPUs in one server and used one of the CPUs for Oracle," recalls Nick van der Zweep, director of virtualization at HP. "Oracle interpreted this as using eight CPUs, and so wanted HP to pay for eight licenses." Since then, Oracle has developed a virtualization licensing policy that resolves such issues. "They've come a long way," he says. "Now, technology can limit applications," he explains, so they run only on the number of CPUs to which they are licensed. Not all companies have resolved the issue, though.

Licensing strategies also affect the choice of virtualization applications themselves, Biddlecombe says. VMware let him run more virtual servers than the competition in the same physical space.  Additionally, "If I need more computing power than a virtual server will provide, I don't virtualize," he says. He doesn't virtualize fax servers, either, or applications that need security keys.

Existing contracts also affect the virtualization decision, van der Zweep points out.  Changing the terms of a managed service contract, for example, can results in additional charges to the company that could negate the cost advantages of virtualization. Consequently, companies sometimes must defer virtualization until key contracts have expired.

Virtualization wasn't the ultimate goal for third party logistics firm Transplace. Instead, it simply wanted more space for its data center.  Acting on that need unearthed other opportunities for operational enhancements that, ultimately, resulted in a data center that is 90 percent virtualized. Virtualization, in this case, was the result of the search for efficiency and increased space. And, van der Zweep opines, that is as it should be. "Don't consolidate just as a way to save money," he admonishes. Instead, virtualize because it makes sense for the business users as well as for the IT operations. "People want agility," he says, and virtualization can offer that.

Although companies typically think first of virtualizing servers, storage and applications, many also are beginning to consider desktop virtualization.   When IT managers look at the needs of users, they fall into three categories, according to Eran Heyman, founder and CEO of Ericom. Task-based users need one to two applications routinely. General purpose users need more complete virtualization services that involve configuration options. Power users need their own dedicated hardware for bandwidth or processing power. All can benefit from desktopvirtualization.

User Needs

"Look at the needs of users," emphasizes Ilan Paretsky, VP of marketing for Ericom. There is a need for a ubiquitous environment that handles legacy applications as well as the early, often cutting-edge development work, throughout the enterprise. To do this, Ericom offers a broad support platform that provides the environments users need and the access and manageability that IT administrators require. "One management console provides the interface to control, manage and provision all of these environments," Paretsky emphasizes, noting that it supports 17 different hypervisors. Ericom's approach offers a broad support platform with one management console and one interface.

Desktops

Desktop virtualization has at least three other aspects, too, that must be considered when deciding what to virtualize.  First, Heyman points out, it's faster and easier to provision virtual desktops from one console than to provision each physical system.  Secondly, security for enterprise systems is more robust than that used on individual desktop or laptop machines. Additionally, by causing the information to reside on a virtual layer off the individual machine, lost laptops no longer pose a significant security risk. Virtualized workspaces also mean that business users can access their own workspace easily from any computer, thus potentially enhancing productivity.

Those are all important considerations that may be easily overlooked if IT administrators assess virtualization only from their own viewpoints. "Before you start, look at the situation from both a technological perspective and an organization perspective," advises Yiping Ding, VP of R&D for systems modeling solutions at OPNET. If mission critical applications are virtualized, will they be immune to failure? Determine whether virtualization make them more, or less, reliable. Also, consider whether virtualized applications will work well together. Not all will, he points out.

Consider Overhead

The question sometimes is less about whether an application should be virtualized as it is about how it should be virtualized. For example, financial and other time sensitive transactions must be assured priority over interactions in which time is not critical. Likewise, mission-critical activities must have assured priority over non-mission critical activities.

In determining what to virtualize," complexity and overhead tend to be overlooked," Ding says. Virtualization involves adding one more piece of software atop a machine. "You have to manage it," he notes. And, HP's van der Zweep adds, certain applications are affected more than others."

Ding compartmentalizes overhead into three broad components - basic technology, the function of partitions and load. They all must be considered. "There's no free lunch," he quips. "The more you do, the higher the overhead."

 Some applications may have noticeable utilization spikes for which virtual resources must be instantly available. Network utilization, for instance, is "very bursty" he says, so a 10 to 20 percent utilization rate must be able to jump to 50 to 80 percent smoothly and instantaneously. Managers also need to consider whether their virtualization strategy can handle seasonal peaks of interest

I/O considerations also should figure into the virtualization decision, Ding insists. "If you consolidate five machines into one, and that one machine has one I/O channel, it becomes a bottleneck. So, make sure you have enough channels!" That's true for network bandwidth, too. And, sometimes, virtualized operations run slower than non-virtualized operations because high memory requirements increase CPU overhead.

To manage that overhead, Ding advises reviewing historical data regarding hardware and applications to identify usage patterns, but cautions that historical data can't provide the entire picture " Change modeling and capacity planning exercises can provide a better understanding of how virtualization will affect a given system and the application in question.  IT administrators need a profile of the environment to help them run the "what if?" scenarios.  

Test First

Analyses should include assessments of the affect on internal users - the IT administrators and support staff - and the external, business unit users. For the business units, virtualization should be transparent. OPNET's "Virtual Machine Quick Predict" application is designed to help IT managers assess virtualization options. Rather than tracking metrics, it accesses memory to help users meet service level objectives and make virtualization recommendations.

Ding recommends establishing a utilization profile over the course of one day - or at least several hours - to establish a baseline for typical activities. His Quick Predict application includes a hardware listing, from which users pick the hardware they intend to use, so they can run analyses using the parameters of the intended equipment at the selected location within the existing environment. Other options are available, too. UUH employed HP's OpenView Internet Services to "record a macro that simulates what a user would do," Peterson says. The application times each transaction and compares the virtual test with benchmarks and makes recommendations. HP also offers assessment services through its consultancy.

Ericom , Transplace , Gartner Group , HP , OPNET , Lights Out and the Path to Enlightenment