Desktop Virtualisation

If you have visited the Server Virtualisation page, you will know that a server consists of Hardware, Operating System and Software Applications. This is equally true of a PC - not surprisingly when you consider Industry Standard Servers evolved from PC's. So in exactly the same way that a server can be virtualised by encapsulating the Operating System and Software Applications into a Virtual Machine - so can a PC.

The Virtual Machines produced in this way can reside within a Physical Server alongside other Virtual Machines - which could be derived from other PC's or other servers. The Hypervisor provides access to the computing resources within the host server - processing power, memory, storage and networking.

A PC which is virtualised in this way retains all the attributes of the original PC's software. So for example, it may be a PC running Windows 7 with Microsoft Office installed and the user login credentials for Joe Bloggs who also wants a picture of his car as the background. So far so good. However, there is a fundamental difference between Joe's physical PC and his new virtual PC. It is virtual - how does he sit in front of it and use it?

The answer lies within some of the remote access technology which allows server based computing to work. The Microsoft version is called Remote Desktop Protocol (RDP) and it allows remote users to access a server and control it as if they were sitting in front of it. Keyboard and mouse inputs and display outputs are redirected to the remote devices over the network. With Virtual Desktop Infrastructure - users can remotely access their virtual machines using either a Thin Client device or a physical PC, laptop or even a Tablet. Alternative "connection protocols" to RDP are used by some Thin Client and VDI providers to improve the user experience (see Marketplace below) - especially to help overcome limitations around video and multi-media and also remote connection of external devices through USB (for example cameras).

Virtual Desktops have caught the imagination of IT departments and businesses for a number of reasons:

• Virtualisation of servers has brought significant benefits meaning the term "virtualisation" is perhaps synonymous with "goodness" wherever it is used

• Thin Clients, which can replace PC's in a VDI are available at a fraction of the cost of PC's, consume much less power, last many years longer (no moving parts), don't go obsolete so quickly and are far easier (cheaper) to manage

• A Virtual PC can run an older version of an operating system - even if it is no longer supported on today's physical hardware. This can provide a way for certain older applications to remain in service.

• Virtual Machines and their data reside within the physical host server - under the control of IT. Users can get remote access to their personal VM's from anywhere using any device which can run the appropriate terminal software. So now workers can access their work PC from home or anywhere else, 24 hours a day with no data security implications (perhaps even using their own personal laptops, PC's or even tablet devices).

The Cloud
One of the advantages of virtual machines is that they can be moved from one host server to another seamlessly. This is true of virtual servers and desktops. So we have a situation where users can be anywhere due to the remote access nature of VDI - and the virtual machines could also be anywhere within the server infrastructure. A logical extension to this is - why not move the VM's onto someone else's servers? The someone else would have to be a trusted partner - so could be a managed service hosting provider with a contract in place which ensures they protect the data and ensure the virtual machines are available to users and perform in line with the businesses needs. This is now a perfectly valid option. The fact that the user's computing needs are coming from IT resources which are unknown - inside or outside of their organisation - makes the whole situation nebulus - something you cannot accurately draw - just like a cloud! Cloud Computing, because of its vague connotations, has become an umbrella term for may aspects of computing but loosely describes systems in which service provision leads the design process - rather than product implementation which is the traditional approach. Virtualisation is one of the key technologies which enables this change in approach.

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