A Quick History Lesson: One of the hottest technologies in the I.T. industry at the moment is virtualisation. Whether it be server, desktop, application or even storage virtualisation, it seems that nearly every vendor has a virtualisation product or technology on offer. But what is virtualisation exactly?

Well, you might be surprised to learn that virtualisation is nothing new technologically speaking. Virtualisation was first implemented more than 30 years ago. As mainframes were expensive resources at the time, IBM designed their mainframes to be logically partitioned into separate virtual machines as a way to fully leverage customer investment.

However more recently, the definition of virtualisation has shifted and its importance has increased dramatically. Now, virtualisation is primarily about disconnecting the application (and infrastructure software) from the hardware platform and, paradoxically, this has made the mainframe a more valuable and more applicable platform than ever.

Virtualisation was effectively abandoned during the 1980s and 1990s when client-server applications and inexpensive x86 servers and desktops led to the introduction of distributed computing. The wide-spread adoption of Windows in the 1990s not only established x86 servers as the industry standard, but along with every increasing speeds of processors has today presented the I.T. industry with a new set of problems to deal with.

With hosting facilities and corporate server rooms bursting at the seams with underutilised x86 servers, it seems every vendor has some unique software that requires a stand-alone server fuelling the growth in server ownership. Today we are faced with increasing energy costs to power these money and resource sucking machines.

It seems that server rooms are the energy vampires of technology's new millennium outstripping even the airline industry in terms of carbon footprint.

x86 Server Virtualisation

According to Wikipedia, x86 virtualisation is defined as:

‘In computing, x86 virtualization provides software based emulation of x86 processor hardware. A "guest" or "virtual" OS may run as a process on a "host" or "physical" system with little or no modification to the guest OS. A virtual machine (VM) is an environment created by a virtualiser (such as Vmware vSphere). Guest operating systems run on virtual machines.’

Or put simply, virtualisation allows organisations to reliably run multiple operating systems on a single x86 host, allowing us to reduce the number of x86 servers owned and deployed. Thereby addressing some of the issues associated with the rapid and uncontrolled deployment of x86 servers.

How Does It Work?

The Hypervisor software component transforms or “virtualises” the hardware resources of an x86 based computer including the CPU, RAM, hard disk and network controller to create a fully functional virtual machine that can run its own operating system and applications just like a “real” computer.

Each virtual machine contains a complete system, eliminating potential conflicts. Virtualisation works by inserting a thin layer of software directly on the computer hardware or on a host operating system. This contains a virtual machine monitor or “hypervisor” that allocates hardware resources dynamically and transparently. Multiple operating systems run concurrently on a single physical computer and share hardware resources with each other. By encapsulating an entire machine, including CPU, memory, operating system, and network devices, a virtual machine is completely compatible with all standard x86 operating systems, applications, and device drivers.

Unlike mainframes, x86 machines were not designed to support full virtualisation. The basic function of most CPUs, both in mainframes and in PCs, is to execute a sequence of stored instructions. In x86 based processors, there are a number of processor instructions that create problems when virtualised. The Hypervisor, a core component of all virtualisation technologies regardless of vendor, traps these instructions allowing x86 servers to become virtualisation hosts.

The illustration below shows a ‘before and after’ image of virtualisation including the location of the Hypervisor.

Other Virtualisation Usages

Apart from server consolidation and all the benefits this brings, virtualisation has many other uses. These range from providing a foundation for business continuity to providing an elegant and dynamic way for deploying desktop services. Uses include:

Infrastructure Provisioning: Reduce the time for provisioning new infrastructure to minutes with sophisticated automation capabilities;

Server Consolidation and Containment: Eliminate server sprawl by deploying systems into virtual machines;

Business Continuity: Reduce the cost and complexity of business continuity by encapsulating entire systems files that can be replicated and restored onto any target server;

Test and Development: Rapidly provision and re-provision test and development servers; store libraries of pre-configured test machines;

Enterprise Desktop (VDI): Secure unmanaged PCs. Alternatively, provide standardized enterprise desktop environments hosted on servers;

Legacy Application Re-hosting: Migrate legacy operating systems and software applications to virtual machines running on new hardware for better reliability.

By Steve Tron
Technology Strategist - Knowledge I.T.