What is Virtualisation?

Alistair McLaurin, principal consultant with IT optimisation consultancy firm Intergence talks us through the nuts and bolts of virtualisation.

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What is Virtualisation? McLaurin says that virtualisation has a host of benefits for enterprises.
By  Alistair McLaurin Published  June 19, 2012

Alistair McLaurin, principal consultant with IT optimisation consultancy firm Intergence talks us through the nuts and bolts of virtualisation.

IT virtualisation refers to the separation of the resources of a physical server from the operating system running on it. Traditionally when an operating system is installed on a PC or server it has exclusive use of the hardware it runs on. When it’s booted up it takes control of the processor, memory and interfaces of that server. Two generations of hardware ago that would have made perfect sense; both PCs and servers had power which matched the operating systems of the day. As the hardware evolved operating systems evolved too, their ability to multi task and run many applications simultaneously became more and more sophisticated.

However, computing hardware has continued to grow in power. Both PCs and servers have increased in power beyond what is required for many business applications. In particular, modern processors with many processor cores and multi-threading are often difficult to utilise to their full potential unless software is specially crafted to utilise their capabilities.

While some applications such as data warehouses can still soak up huge quantities of dedicated server capacity, many standard enterprise applications, infrastructure services and desktop applications cannot consume all the resources that are available to them.

Many businesses are also concerned about the security and performance of their core applications and prefer not to have them share an operating system with other applications, to protect confidential data or to ensure guaranteed performance at all times.

This is where virtualisation comes in. A virtual machine or hypervisor is first installed on a PC or server which interfaces with all the physical components of the hardware it is installed on. It then creates anything from one to hundreds of virtual machines which real operating systems can be installed into.

These virtual machines generally are allocated a slice of the physical server’s resources, for example a six core processor may be split into six virtual processors or a gigabit network interface may be split into many virtual network interfaces.

As an operating system is installed into these virtual machines it sees the resources the hypervisor is giving to it, as if it was a physical machine, and installs just as it would on a physical machine.

Everything is self-contained without virtual machines being aware of the existence of anything else on the same hardware.

While there can be slight overhead of CPU and memory to support running the hypervisor, this is generally very low as the hypervisor does its work as a system boots up and then gets out of the way.

A further benefit of using hypervisors is that virtual machines can always be created with the same specifications in terms of processor power, memory, and network access.

This means that organisations can buy the best hardware on offer to them at the time without having to retest and rebuild applications and operating systems for new hardware configurations.

The new hardware is simply configured to support the standard virtual machines. In addition, operating systems can be created and deployed as images for standardised virtual machines, a process which takes seconds rather than hours for a new install. Increasingly operating system vendors, particularly Linux vendors, can supply pre built OS images for your use.

This concept has also extended to the concept of a virtual appliance where data centre components such as load balancers, firewalls and caching proxies are supplied as ‘virtual appliances’, software images which can be loaded on to virtual machines rather than physical servers and be available for use in minutes.

Virtualisation use cases
Another use case for virtualisation is the provision of virtual desktops. Here, concentrated server power such as a blade chassis are divided into hundreds or thousands of virtual machines with a similar specification to a desktop PC.
These then have a desktop operating system and applications installed on them to interface with the corporate network. This opens up a large number of possibilities.

A company can use thin clients or low end PCs to access desktops which offer higher power or a more managed environment. Alternatively these solutions can be deployed for remote or travelling workers to allow access to the corporate network, with security being enforced by access to the desktop and the applications which can be run on the virtual desktop.

A final use case for virtualisation is to allow running multiple operating systems on a desktop. This is a model which first become widespread with the introduction of Intel based Apple Macintoshes which led to a boom in people using virtualisation on the Macintosh to run Mac intosh and Microsoft Windows side by side. We are now seeing people using similar software to run Windows and Linux on the same computer, allowing them to use corporate standard Windows applications combined with a range of open source engineering, development applications and environments.

Real benefits
So, virtualisation can offer real benefits to any organisation at every level, from server farm optimisation to supporting an enterprises remote workers. It is also a field where vendor offerings continue to develop at a rapid pace and organisations need to look for standards support to ensure they do not become locked into proprietary single vendor solutions.

To be successful, an organisation will need to ensure their monitoring and management systems are updated to ensure they have the ability to visualise the mixture of physical and virtual servers that we will all be using and managing in the not-to-distant future.

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