Virtualisation gets trendy

Virtualisation is not just about servers anymore. Quocirca's Dennis Szubert explains the many uses of this paradigm-shifting technology.

Had you 'Rip van Winkled' your way through the first half of this decade, you could have fallen asleep thinking virtualisation was merely a means of slicing-up large servers. However you would have awoken to discover it is in fact one of the most versatile tools in IT.

Virtualisation is now involved in the most trendy fields in the industry including data centre automation, utility computing, green computing, security, business continuity, blades, grid and SOA.

Just like an iceberg with 90 per cent of its bulk below the surface, the massive impact virtualisation will have on IT has been largely hidden and is only now becoming widely appreciated.

What is virtualisation?

IBM first announced VM/370 virtualisation in 1972 but had been using the technology internally years earlier. They originally used it to partition a server to consolidate numerous smaller servers - and for most people this is probably the first thing that springs to mind when the word is mentioned.

However, apart from server virtualisation you can also have storage virtualisation, network virtualisation, desktop virtualisation and even application (or service) virtualisation.

In general terms, virtualisation refers to the abstraction of computer resources so they can be logically assigned. It is a technique for hiding the physical characteristics of computing resources from the way in which other systems, applications or end users interact with those resources.

It has two main forms. Partioning (or zoning) is the splitting of a single, usually large resource into a number of smaller more easily utilised resources of the same type. Aggregation (or concatenation) is the combining of individual components into larger resources or resource pools.

An example of the first kind of virtualisation is partitioning a PC disk into smaller virtual drives, while an example of the second is combining a number of separate disks to make them appear as one physical disk (as in a storage network).

Grid computing is also an example of resource aggregation, as it enables the virtualisation of distributed IT resources such as storage, bandwidth and CPU cycles, while splitting a mainframe into logical partitions is an example of partitioning.

While the term virtualisation has been around since at least the 1960s, recent developments have refocused attention on the concept - thanks in part to husband and wife team Diane Greene and Mendel Rosenblum who founded the company VMware.

They released a desktop virtualisation product in 1999, followed by one for servers in 2001. In so doing, they brought virtualisation out of the mainframe glasshouse and onto industry-standard x86 hardware which had never been designed to be virtualised.

How is it used?

Some of the more basic uses of virtualisations have already been discussed but it is now being adopted in a wide range of areas including:

• Virtual infrastructure

  By 2003 VMware realised the killer-app for virtualisation was not consolidation alone but the ability to produce flexible, shared resource pools. Couple server virtualisation with virtualisation of the storage and the network connections, and what you get is a 'virtual infrastructure'.

  As the underlying technology became more pervasive and competition began to emerge, VMware shifted its focus onto the possible uses. Partition mobility (or VM mobility) - the ability to move running virtual servers between physical servers without service interruption - is key to the ability to produce an always-on, flexible shared-services infrastructure. With this, all kinds of solutions - high availability, disaster recovery, consolidated back-up - become possible and enable the next generation computing environment: the optimised data centre.

• Application development and distribution

  Desktop virtualisation, allowing multiple OSes and software versions to run in different windows on the same PC, can increase productivity for software developers and testers by allowing them to create or test applications for multiple software configurations on one machine.

  Virtual appliances - 'freeze-dried' software stacks of OS, middleware and application, certified to run together and packaged as a single virtual machine - is an appealing distribution vehicle for software, bearing in mind that most installation problems are configuration related.

  In application design, SOA can be thought of as application virtualisation, as it abstracts application functionality into a service component layer.

• Security

  The ability to provide standardised and secure PC environments as virtual machines has appeal not only to corporate IT administrators ('no YouTube for you!') but conceivably also to banks who could, for example, create a virtual machine for customers with a stripped-down OS and browser that can only access the online banking site.

The fact that so many areas of IT are affected by virtualisation is perhaps testament to how fundamental a concept it is to separate computer resource from the underlying physical hardware - and demonstrates this is a strategic issue with a broad impact that has to be considered at the highest levels of IT management.