In the previous instalment of this article, the two fundamental models of cloud computing, private and public clouds, were described. The following installment introduces two further variations on these models which can be used to add flexibility to an organisationâ€™s IT infrastructure, the hybrid and the community cloud models. Community Cloud A community cloud model describes a scenario in which a number of organisations with similar IT demands club together to use the same cloud infrastructure. They are particularly appropriate where the organisations perform similar functions and therefore require the same configurations, especially in relation to security and compliance. In essence it is a half-way house between the private and public cloud models. The model is similar to that of a private cloud in that it is a ring fenced platform which ensures greater levels of security than the public cloud offers and it can also be hosted internally by the constituent organisations to ensure greater ownership and control (at the expense of some cost savings). However, because it has multiple clients (usually a small number) it also provides economies of scale which are missing in private clouds and therefore greater cost savings than the individual equivalents. Furthermore, in common with a public cloud model, organisations can take advantage of pay as you go pricing structures. Hybrid Cloud The hybrid model of cloud computing is also somewhat self explanatory in that it is used to describe any configuration which utilises a combination of the public and private cloud computing models, or indeed a combination involving community cloud models. It comes under the slightly broader categorisation of hybrid IT – that is an IT platform which integrates a mixture of internal and external networks and services so that the resource being used can provide the maximum benefit for each business function. Hybrid cloud models can therefore give an organisation access to the differing benefits of public and private models, primarily cost/scalability and security respectively, as and when they need them by integrating the different models for the different functions within the organisation. For example, a business that processes and stores sensitive data may do so on a private cloud platform to ensure that it is secure whilst also taking advantage of the scalability of a virtualised environment. It may then use integrated public cloud services for all of the less sensitive functions, such as project planning, in order to benefit from the considerable costs savings and scalability that that can bring. A hybrid cloud set-up, like hybrid cloud hosting, can be constructed in a couple of ways: either by providers of each model of cloud computing teaming up to provide a hybrid platform which organisations can sign up to to perform their differing IT functions; or by an organisation managing their own internal private cloud or other IT infrastructure and then signing up to an integrated external public cloud service where they can, to handle their non data sensitive functions. Whatever a clientâ€™s computing needs, there will be a cloud based service to meet their demand and provide that client with the benefits of virtualisation and utility style computing; including responsive on-demand scalability, cost efficiencies (including pay as you go and free services) and redundancy. By becoming aware of the potential of using public, private and community clouds as well as the hybrid models which combine and maximise the benefits of each, organisations can ensure that they keep their IT operations as efficient, productive and secure as possible.