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How to Set Up a Virtualization Server - PCWorld Business Center

By Paul Venezia, PCWorld

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If there's one technology that can greatly improve computing environments of any size, it's virtualization. By using a single physical server to run many virtual servers, you can decrease operational costs and get far more bang for your buck. Whether your company is a 2-server or 2000-server shop, you can benefit from server virtualization in a variety of ways. The best part? You can do it cheaply and easily.

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How to Move From a Physical to Virtual Infrastructure
The reasons to virtualize even a small infrastructure come down to ease of administration and cost reductions. Cost reductions come from cutting down the number of physical servers, thus reducing the power and cooling requirements, but they also come in the form of greatly reduced expansion. Rather than having to purchase new hardware to support a new business application, all you need to do is add a new virtual server.

If your business has only a single server, virtualization isn't likely to buy you much, but if you have more than two servers or if you plan on expanding anytime soon, virtualization can likely make a difference.

It's impossible to purchase a server today that isn't multicore, but many small-business server requirements simply don't call for that much horsepower. The end result is a relatively expensive server that does very little but still consumes power and generates heat. That's why using a multicore server--that is, a server that has 4, 6, or 12 processing cores on a single CPU--to host several virtual servers makes sense, no matter what size your company is.

The Host Server

The key to successfully virtualizing servers in a smaller environment starts with the physical host server, the box that will run multiple virtual servers. Even though this one server will be responsible for hosting possibly dozens of virtual servers, it will require far fewer CPU resources than you might assume.

Depending on the virtualization software in use--VMware, Microsoft's Hyper-V, Citrix XenServer, or another package--you will likely be able to run a surprising number of virtual servers on a four- or six-core CPU. The reason is that generally most servers run near idle a significant portion of the time. When they are tasked with work, their resources tend to be spread out among the RAM, CPU, disk, and network input/output, with only a subset of the virtual servers actually requiring significant CPU resources. By taking advantage of this law of averages, you can consolidate a considerable number of physical servers onto a single host server.

That isn't a hard and fast rule, however. Some servers, such as database servers, run heavier loads on a more consistent basis, and may not be suitable candidates for virtualization in a smaller infrastructure. It all depends on the hardware resources available to the host server, on the virtualization software features, and on the requirements of the virtual server. Fortunately, setting up and testing these requirements beforehand isn't difficult.

The first order of business when approaching a small virtualization project is to choose the hardware. Generally you'll start out with only a single server, so try to get the best mix of resources possible within budget.

A good rule of thumb is that having more cores in the host server trumps higher clock speeds, so if you have a choice between a 4-core CPU running at 2.93GHz and a 6- or 12-core CPU running at 2.4GHz, you'll be better off with the latter option. That's because the capability to spread the virtual-server load across more CPU cores typically translates into faster, more consistent performance across all the virtual machines. Think of it as needing a dump truck (which isn't that fast) instead of a sports car (which is faster but can haul far less than the dump trunk can).

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