Green IT Book Excerpt: Virtualizing Your Systems - InformationWeek

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5/13/2009
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Green IT Book Excerpt: Virtualizing Your Systems

This chapter of The Greening Of IT: How Companies Can Make A Difference For The Environment, explains the concepts of virtual servers and virtual data storage for energy-efficient data centers.

The advent of ubiquitous high-speed networks has eliminated the need for a server in the same building. These days, network access even to our homes through high-speed networks such as DSL and cable allows network performance from our homes or distributed offices to the central data center to be about equivalent to performance when your office is in the same building as the data center.

The Internet was and remains the most-significant driving force behind the availability of high-speed networks everywhere in the world -- including to homes in most of the developed world. When we access a Web site from our home, from the airport with a wireless connection, or from the countryside using a PDA or an air card with our laptop, we have a high-speed connection to a server in some data center. If the Web site is a popular site such as Google, the connection might be routed to any one of many large data centers.

When the distributed servers that had been in office buildings were moved in the past ten years to centralized data centers, operations and maintenance became greatly simplified. With a company server at a centralized data center, you could now call the help desk on Sunday morning and find out why you had no access, and central operations could have atechnician "reboot" the server if it had gone down.

So, the centralized data center provides many advantages -- especially with high-speed networks that eliminate network performance concerns. However, with the rapid growth in servers used in business, entertainment, and communications, the typical data center grew from dozens of separate physical servers to hundreds of servers, and sometimes to thousands.

Purchasing, operating, and maintaining hundreds of separate physical servers became expensive. The innovative solution was to consolidate perhaps ten of the separate servers into one bigger physical server, but make it appear as if there were still ten separate servers. Each of the ten virtual servers could retain its own server name, its own Internet®address (IP address) and appear -- even to web developers -- to be a separate physical machine (as it had been before becoming a virtual server).

Costs go way down because one large physical box is much less expensive to buy than ten smaller physical boxes. Also, it's significantly less expensive to maintain and operate ("take care of") one big server than ten smaller servers. The analogy might be exaggerated -- but it's a bit like taking care of one big house rather than ten separate smaller houses.

In simple terms, server virtualization offers a way to help consolidate a large number of individual small machines on one larger server, easing manageability and more efficiently using system resources by allowing them to be prioritized and allocated to the workloads needing them most at any given point in time. Thus, you can reduce the need to over-provision for individual workload spikes.

In general, virtualization at the data center is applied broadly -- not just to server virtualization. It provides the capability to simulate the availability of hardware that might not be present in a sufficient amount -- or at all! Virtualization uses the available physical resources as a shared pool to emulate missing physical resources.

Virtualization is capable of fine control over how and to what extent a physical resource is used by a specific virtual machine or server. Thus, we have the concept of virtual computer memory (which is not real memory but appears to be real) and virtual data storage.

This chapter gives details on virtualization technologies at the data center and explains how those technologies are usually the first and most-important step we can take in creating energy-efficient and green data centers.

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