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Virtualisation Overview
By: Roel Gloudemans et. al. (2008)
Virtualisation is the technique of relating physical computer resources to logical definitions of those same resources, for the purpose of providing a business service with its own optimised, stable and independent IT environment.
There are various technologies and vendor products available to achieve virtualisation, including Xen and VMWare. These products comprise a tool called the Hypervisor, whose task is to map logical resources onto physical resources, and a virtual machine manager which organises and controls the logical subgroups of computer resources, known as domains or virtual machines.
Advantages of virtualisation include the need for fewer machines through better utilisation of hardware capacity, thereby reducing hardware, software licence and energy costs. Adjusting air conditioning capacity accordingly will further reduce environmental impact. Because of the virtual nature of the domains, they can be moved with relative ease between machines to facilitate maintenance without interrupting the business service. Performance and demand management are also relatively easy to effect, through adding and removing resources from computer environments as required.
The main areas of concern regarding virtualisation are the inherent security risks, and the greater potential impact of component failure as a result of clustering business services on fewer hardware units. The presence of a virtual machine manager within a hardware system provides a target for attacks on system security. The architecture of the IT environment and organisation needs to be holistically designed and developed in order to eliminate potential weaknesses. Proactive management and maintenance of the IT systems alongside insight in the business relevance of specific components (and impact of component failure) is also essential in the successful deployment of virtualisation. Virtualisation (especially within the context of a Service Oriented Architecture programme) can contribute to the professionalization of an IT service organisation.
