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Virtualization software or blade servers: Which is right for server consolidation?

Considering an investment in virtualization software or blade servers to manage server room sprawl? David Marshall, author of a new book on advanced server virtualization, discusses the merits of both technologies for server consolidation.

Want to consolidate in the server room, but not sure if virtualization is right for your shop? Are you considering investing in blade servers, but want to make sure you will get the most bang for your hardware buck? news writer Joan Goodchild discusses the pros and cons of both technologies with David Marshall, senior architect at Surgient Inc., and co-author of the forthcoming book Advanced Server Virtualization: VMware and Microsoft Platforms in the Virtual Data Center (Auerbach Publications, 2006). When considering options for server consolidation, many IT managers consolidate with blade servers, others use virtualization technology. Could you explain the difference between the two?

David Marshall: IT managers are currently being faced with a growing pressure to consolidate the data center. Some of the biggest challenges facing today's IT managers deal with power, heat, cooling and system density -- all challenges that server consolidation hopes to eliminate in some way. Both technologies, blades and virtualization, are attempting to solve this problem.

The basic difference between the two solutions and the most simplistic answer is that one, blade servers, is a hardware-based solution, while the second, virtualization, is a software-based solution. A blade solution is a small-sized, modular server; and each server has its own processors and memory, but shares power supplies, cooling, interconnects, cabling and storage. By packing multiple server blades inside a standard enclosure, a higher density is achieved.

Virtualization, on the other hand, pools a server's resources and then slices them up and allocates those resources to virtual machines so that the resources are then used more efficiently and can be stretched further. Another simplified difference is that blades require an investment in infrastructure and equipment, while virtualization requires an investment in software but tries to use existing hardware where it can.

Are blades and virtualization competing against one another? Or do they serve different types of consolidation needs?

Marshall: You'll get different answers from different people on this one. I believe that blade servers have their place and virtualization solutions have their place. People have found value with both solutions in their own respective environments and use cases. And, at some point along the way, there is an intersection where these two solutions meet and can be combined to solve other unique problems.

In general, though, I still believe that ultimately these solutions are attempting to solve some of the same problems. However, these solutions also offer so much more than just meeting consolidation needs. In discussing consolidation, both products attempt to correct data center space problems, power consumption, cable management and ease of use and replacement. In that respect, they may not directly compete with one another, but they certainly step on each other's toes.

Who would choose blades? Who would choose virtualization? Do they work together?

Marshall: Since the blade solution is typically a hardware solution, those companies that are at the point where they need to invest in new infrastructure hardware and server equipment might typically go down the blade route. While upgrading to a blade solution is significantly different than just upgrading from one brick server to a newer version of the same server, migrating to different hardware is typically an easier pill to swallow for a data center IT guy. [It's easier] than moving to a whole new methodology involving software, such as a virtualization platform.

However, if you have an existing data center that is made up of hardware that can be reused -- and by reused I mean servers that are typically being underutilized -- then those IT managers may choose to go down the route of choosing virtualization.

Keep in mind, blades and virtualization do not have to be mutually exclusive. The two solutions can work together. In fact, the two are often marketed together by their respective vendors.

In certain circumstances, it might make sense to use the two technologies together, where they would complement each other rather than be competitive. One drawback: Blades are just now starting to expand their capabilities.

When consolidating with virtualization, like ESX Server for example, you typically want a beefy box with plenty of available network adapters, processors and RAM. Although blades are getting there, they typically can't produce the numbers that brick servers offer.

When trying to explain to someone which would be the best choice for consolidation, what advice would you give them?

Marshall: It really depends on their specific problems and needs. Unfortunately, consolidation of a data center or computer infrastructure can be drastically different from one location to the next. If you don't have any in-house expertise on the subject, I would highly recommend that you get advice from a third-party consultant. Choosing a blade solution or a virtualization platform to perform a data center consolidation without proper planning or an understanding of either technology can lead to unnecessary downtime and huge monetary costs. It's a rabbit hole that you don't want to go down unless you've properly mapped it out.

Neither solution is perfect. As an example, you might have a group of servers that are way under-utilized. Those are good candidates to consolidate through virtualization. But, if you have a server that is already hitting 80% or more utilization, you probably don't want to virtualize it.

What do you see in the future with regard to both blade and virtualization technologies?

Marshall: Virtualization technologies have really taken off this year. New virtualization platforms are being created; and hardware is being released to help push virtualization performance and robustness forward. The technology is really starting to mature, open up and expand across the IT community into different realms.

In my opinion, blades are just now starting to come into their own. Early adopters found problems, and the vendors are really starting to address those problems and other needs by adding features and expanding their hardware limitations.

Blades, virtualization and a third comparative newcomer, grid computing, will eventually merge to provide a dynamic and powerful infrastructure. Once all three technologies mature to a certain point, their differences and complementary technologies will form a synergy that will change the way computing and data centers operate in tomorrow's world.

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