A private cloud is a particular model of cloud computing that involves a distinct and secure cloud based environment in which only the specified client can operate. As with other cloud models, private clouds will provide computing power as a service within a virtualised environment using an underlying pool of physical computing resource. However, under the private cloud model, the cloud (the pool of resource) is only accessible by a single organisation providing that organisation with greater control and privacy.
The technical mechanisms used to provide the different services which can be classed as being private cloud services can vary considerably and so it is hard to define what constitutes a private cloud from a technical aspect. Instead such services are usually categorised by the features that they offer to their client.
Traits that characterise private clouds include the ring fencing of a cloud for the sole use of one organisation and higher levels of network security. They can be defined in contrast to a public cloud which has multiple clients accessing virtualised services which all draw their resource from the same pool of servers across public networks. Private cloud services draw their resource from a dsitinct pool of physical computers but these may be hosted internally or externally and may be accessed across private leased lines or secure encrypted connections via public networks.
The additional security offered by the ring fenced cloud model is ideal for any organisation, including enterprise, that needs to store and process private data or carry out sensitive tasks. For example, a private cloud service could be utilised by a financial company that is required by regulation to store sensitive data internally and who will still want to benefit from some of the advantages of cloud computing within their business infrastructure, such as on demand resource allocation.
The private cloud model is closer to the more traditional model of individual local access networks (LANs) used in the past by enterprise but with the added advantages of virtualisation.
The features and benefits of private clouds therefore are:The most recognisable model of cloud computing to many consumers is the public cloud model, under which cloud services are provided in a virtualised environment,constructed using pooled shared physical resources, and accessible over a public network such as the internet. To some extent they can be defined in contrast to private clouds which ring-fence the pool of underlying computing resources, creating a distinct cloud platform to which only a single organisation has access. Public clouds, however, provide services to multiple clients using the same shared infrastructure.
The most salient examples of cloud computing tend to fall into the public cloud model because they are, by definition, publicly available. Software as a Service (SaaS) offerings such as cloud storage and online office applications are perhaps the most familiar, but widely available Infrastructure as a Service (IaaS) and Platform as a Service (PaaS) offerings, including cloud based web hosting and development environments, can follow the model as well (although all can also exist within private clouds). Public clouds are used extensively in offerings for private individuals who are less likely to need the level of infrastructure and security offered by private clouds. However, enterprise can still utilise public clouds to make their operations significantly more efficient, for example, with the storage of non-sensitive content, online document collaboration and webmail.
The public model offers the following features and benefits:
Location independence: the availability of public cloud services through an internet connection ensures that the services are available wherever the client is located. This provides invaluable opportunities to enterprise such as remote access to IT infrastructure (in case of emergencies etc) or online document collaboration from multiple locations.