Scotland's Digital Future: Scottish Public Sector Data Centre Virtualisation Guidance

What is virtualisation?

Virtualisation can dramatically improve the efficiency and availability of ICT resources and applications in an organisation by moving away from a model of "one server, one application". This enables underutilised resources to be dynamically applied to a number of machines.

Hardware virtualisation or platform virtualisation refers to the creation of a virtual machine ( VM) that acts like a real computer with an operating system.

This is achieved by abstracting a physical server's resources ( CPU, Memory, Networking etc.) and presenting them to each virtual machine that is running on the physical host. By doing this, multiple virtual machines can share the same physical hardware but appear and run as separate servers in the organisation's network.

These virtual machines are commonly known as guests, running on their parent hypervisor (the software or firmware that creates a virtual machine) host running Windows or Linux operating systems (dependent on Hypervisor).

Server virtualisation allows for a more efficient use of resources by removing multiple physical servers, for example Active Directory Domain Controllers and Exchange Servers which traditionally run on separate instances of Windows would not now require separate hardware platforms.

By removing the one to one relationship between a service or application and physical hardware a number of new possibilities are now available to an organisations environment. Services can now be moved as simply as moving a file from one location to another, disaster recovery in minutes rather than hours or days is now possible to achieve at a fraction of the cost it would have been with a physical environment.

To further enhance the basic advantages of less hardware and a flexible moveable virtual machine, virtualisation also brings other advantages for management. These features vary dependent on which hypervisor has been used but features such as below are found in all the leading hypervisors:

• Ability to move virtual machines between hosts and storage whilst running.
• Ability to increase memory and CPU resources.
• Replication of entire virtual machine to another host either locally or remotely.
• High availability allowing for host failure
• Snapshots of running machines providing instant recovery
• Templates providing faster deployment of virtual servers.

These and more features are only possible because of the abstraction of the hardware and software layer that is provided in server Virtualisation.