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July 28, 2006
• Vol.28 Issue 30
Page(s) 29 in print issue
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Pitfalls Of Server Virtualization
Its More Than Just Technical
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Virtualization has come to the forefront recently for several reasons. The potential to save money and to consolidate servers and storage is bound to appeal to any IT manager who works within a budget or has limited space in which to house servers and storage devices (in other words, pretty much everyone). “A few years down the road, virtualization will be the standard, the norm,” says Michael Materie, product line manager for Diskeeper. And Processor’s in-depth coverage of virtualization a few months back (see the “Where To Find More” sidebar for more information) illustrates that SMEs have as much to gain, or more, by incorporating virtualization technology into their networks.
At the same time, “virtualization doesn’t solve the world’s problems,” says Illuminata senior analyst Gordon Haff. “It’s like any technology. There aren’t pitfalls per se so much as caveats to be aware of.”
“You’ve got to know what you’re doing as with any technology. You have to study proper configuration [for your needs] as well as best practices,” says Yankee Group senior analyst Laura DiDio. “The pratfalls come when you are badly configuring or misconfiguring or not following best practices. Virtualization is like fire. Fire’s a good thing, but you don’t carry a lighted match with you at the gas station.”
 Understanding Virtualization
While virtualization technology has been touted as the solution to server sprawl and management, an organization must have a management framework and applications in place if it wants its solution to work, Haff says. When these solutions falter, “it’s not a failure of virtualization per se but a failure to understand components of virtualization and what it can and cannot do.”
Most important perhaps is the understanding that server virtualization is a component of virtualization taken as a whole, Haff continues. Virtualization in the data center encompasses storage and networking as well. Having a sense of the broader scope is necessary to making sure that companies set up and maintain their virtual servers with as few hitches as possible.
“There is great potential to save money using server virtualization, but the amount of cost savings will be determined by the particular configuration and the know-how of those setting it up,” DiDio says. “Some of these things sound facile and straightforward, but there are no shortcuts or silver bullets out there.”
Configuration Basics
First off, make sure your physical components are compatible and robust enough to handle your virtualization needs. In other words, make sure you’re using approved memory and drivers and check with your vendor about the minimum and recommended hardware requirements for the virtual servers you are planning to set up.
“You wouldn’t put a 500-pound man on a Shetland pony, and you can’t put four virtual [Microsoft] SQL Servers on a one-processor or two-processor physical server,” DiDio says.
Haff agrees that monitoring the load placed on your physical servers is essential. “If you install too many applications using virtualization, you may need more resources because even if [the physical server’s] CPU is being underutilized, your memory may not be running these virtual machines, and you may need more resources,” he says.
DiDio adds that running an SME makes it particularly important to get these things right because SMEs typically have less of a cushion than their large counterparts. “If something goes wrong, there’s more of an impact on the business in a very short time. So it’s doubly important [for them] to spend the money and invest the time either to get their internal staff trained or to hire a consultant and a system integrator to set them up,” she says.
Don’t Ignore Licensing Contracts
Virtualization offers huge potential savings in licensing fees, but you must make sure you are familiar with the terms and conditions of your corporate licensing contracts, says DiDio. Otherwise, you may find yourself spending more money inadvertently.
“For example, Microsoft allows you to install SQL Server on up to four virtual servers on a single physical server. If you don’t know or understand licenses, you might be putting four instances on four physical servers insteadand be paying for it,” DiDio cautions.
“The problem is that people who negotiate the licensing contracts are usually not the same people who use them. You have to get your organization working in tandem,” DiDio says.
The Fragging Question
Another issue facing those setting up virtual servers is the increasing disparity between high-performing CPU and memory chips and storage. According to Diskeeper’s Materie, the fastest hard drives available in the mainstream marketplace run at 15,000rpm. In contrast, CPUs and memory are measured in nanoseconds.
According to Materie, server administrators need to look for ways to make the slowest component in the network as fast as possible to alleviate bottlenecks. SMEs can strive for relative parity by employing high-performance hard drive setups. SANs have dropped significantly in price over the last several years, making them affordable for SMEs.
In addition, Materie says that defragmenting storage allows for faster access to data by consolidating file fragments. When the CPU is not searching all over the hard drivebe it virtual or physicalfor pieces of a given file, you can expect quicker performance and a decrease in bottlenecks through I/O channels.
Or Can You?
For his part, Illuminata’s Haff says that the benefits of defragmenting storage in a virtual setup are minimal, even though virtualization has the potential to cause greater disk fragmentation.
“The problem is that CPU and memory are so much faster than disks that optimizing disk speed is like a drop in the proverbial lake,” Haff says. “As a last tweak, optimization sometimes makes cost-effective sense, but it is not a problem standing in the way of adopting virtualization.” 
by Robyn Weisman
Watch Out For These Configuration Issues
According to Michael Materie of Diskeeper, here are some configuration issues to avoid:
• Certain technologies don’t emulate well. Virtual video cards, for example, will not have the functionality of their physical counterpartsand hardware support won’t translate over to the virtual counterpart.
• In host/guest virtualization setups, the host machine views both the user mode and kernel mode in the guest virtual machine as an application; therefore, kernel stuff on the virtual machine becomes user-level stuff, which could lead to havoc if it’s fiddled with. A specialized software architecture called hypervisor, which will be available for Windows Vista Server (it’s already being used on Unix-flavored machines and is available for Windows and Linux OSes in VMware ESX Server), circumvents this problem.
• Don’t overvirtualize your system. Now that your CPU power is being utilized more effectively, make sure you have enough memory to run your applications and get the fastest storage setup you can afford.
• At the same time, never get in a situation where you overtax your CPU. “That’s not a pitfall. That’s just the wrong decision, period,” Materie says. |
Where To Find More
The March 31 issue of Processor’s Cover Focus section focused on virtualization and consolidation. To view these articles online, click the Editorial link in the lower-right corner of the All-In-One Search area on the Processor.com home page. Click Browse All Issues and then click the Virtualization & Consolidation link next to the Mar 31 06 issue listing to view the issue. |
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