Virtualization Defined - Eight Different Ways - White Paper

Short Description
Alice has asked the million-dollar question: What does “going virtual” really mean in today’s IT world? Virtualization as a concept is not new; computational environment virtualization has been around since the fi rst mainframe systems. But recently, the term “virtualization” has become ubiquitous, representing any type of process obfuscation where a process is somehow removed from its physical operating environment. Because of this ambiguity, virtualization can almost be applied to any and all parts of an IT infrastructure. For example, mobile device emulators are a form of virtualization because the hardware platform normally required to run the mobile operating system has been emulated, removing the OS binding from the hardware it was written for. But this is just one example of one type of virtualization; there are many definitions of the term “virtualization” fl oating around in the current lexicon, and all (or at least most) of them are correct, which can be quite confusing.

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Content
Operating System Virtualization
The most prevalent form of virtualization today, virtual operating systems (or virtual machines) are quickly becoming a core component of the IT infrastructure. Generally, this is the form of virtualization end-users are most familiar with. Virtual machines are typically full implementations of standard operating systems, such as Windows Vista or RedHat Enterprise Linux, running simultaneously on the same physical hardware. Virtual Machine Managers (VMMs) manage each virtual machine individually; each OS instance is unaware that 1) it’s virtual and 2) that other virtual operating systems are (or may be) running at the same time. Companies like Microsoft, VMware, Intel, and AMD are leading the way in breaking the physical relationship between an operating system and its native hardware, extending this paradigm into the data center. As the primary driving force, data center consolidation is bringing the benefits of virtual machines to the mainstream market, allowing enterprises to reduce the number of physical machines in their data centers without reducing the number of underlying applications. This trend ultimately saves enterprises money on hardware, co-location fees, rack space, power, cable management, and more.
Application Server Virtualization
Application Server Virtualization has been around since the fi rst load balancer, which explains why “application virtualization” is often used as a synonym for advanced load balancing. The core concept of application server virtualization is best seen with a reverse proxy load balancer: an appliance or service that provides access to many different application services transparently. In a typical deployment, a reverse proxy will host a virtual interface accessible to the end user on the “front end.” On the “back end,” the reverse proxy will load balance a number of different servers and applications such as a web server. The virtual interface—often referred to as a Virtual IP or VIP—is exposed to the outside world, represents itself as the actual web server, and manages the connections to and from the web server as needed. This enables the load balancer to manage multiple web servers or applications as a single instance, providing a more secure and robust topology than one allowing users direct access to individual web servers. This is a one:many (one-to-many) virtualization representation: one server is presented to the world, hiding the availability of multiple servers behind a reverse proxy appliance. Application Server Virtualization can be applied to any (and all) types of application deployments and architectures, from fronting application logic servers to distributing the load between multiple web server platforms, and even all the way back in the data center to the data and storage tiers with database virtualization.
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