What is Cloud Computing?

'The cloud can be what you want it to be; there are many types of cloud and no single model has to be adopted.'

Clark et al 2011

'The cloud' is as nebulous as the name suggests. The term arose from the cloud symbol used in diagrams to represent the internet and 'cloud computing' is used loosely to describe all manner of services delivered via the internet. A very simple parallel for why it may be useful to acquire computing power in this way is perhaps to think of receiving electricity via the National Grid. You don't need to be able to generate and store your own electricity in order to use applications powered by this means and you only pay for the electricity you actually consume. The situation with cloud computing is rather more complex but the analogy serves as a starting point for looking at the potential advantages (explored further in the section on Benefits of Cloud Computing).

You may be wondering whether there is empirical evidence for the potential advantages or whether many of the claims are simply hype. Whilst there are certain risks that need to be understood and managed (see the section on Risks of Cloud Computing), Cloud computing differs from many other hyped technologies. The underlying technologies are mature in themselves and the post-compulsory education sector generally has the bandwidth required to benefit from them via the JANET network. As a result of the perceived benefits, SURF (the Netherlands equivalent to JISC) recommends a policy of 'cloud first' as regards technology options for its member universities and the UK government is promoting cloud as the way forward for the public sector.

One of the most commonly used definitions of cloud computing comes from NIST: the US National Institute of Standards and Technology (Mell & Grance 2009):

'Cloud computing is a model for enabling convenient, on-demand network access to a shared pool of configurable computing resources (eg networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction. This cloud model promotes availability and is composed of five essential characteristics, three service models, and four deployment models.'

The essential characteristics defined by NIST are: On-demand self-service, broad network access, resource pooling, rapid elasticity and measured service. We look further at what these characteristics mean and how they translate into an attractive proposition for the sector in the section on Benefits of Cloud Computing.

Service models relates to which part of the computing infrastructure is actually delivered via the cloud. We look at each of the options: Software as a Service (SaaS) Platform as a Service (PaaS) and Infrastructure as a Service (IaaS) in the section on Cloud Service Models.

Deployment models relates to the extent to which the infrastructure is private to a single organisation or shared with a wider group of other, known or unknown, users. There is a section in this resource on Cloud Deployment Models and many of the Risks of Cloud Computing relate to the choice of model.

The question is not whether we should 'enter the cloud' but when and how that should be.'

SURF 2011

'The basic principle for decisions on new applications is 'cloud first' because using commodity services from the cloud has major advantages.'

SURF 2011

'Clouds do not get clearer as you approach them.'

Katz 2008

Useful Phrases

Cloud-burst

When a private Cloud has a temporary need for additional resources and 'bursts out' into the public Cloud to obtain those resources.

Cloud-jacking

When a 'hacker' takes control of all or part of a Cloud infrastructure. The term is also sometimes used to refer to exploiting and dominating a niche market in the Cloud.

Cloud-sourcing

Replacing traditional IT services with cloud services.

Cloud-storming

Connecting multiple Cloud computing environments.

Cloud-wash

Marketing hype that tries to make an existing product sound as if it is new and different by making reference to the Cloud.

Vapourware

A much older term and not specifically related to the Cloud: refers to future, improved, versions of a software application that may never actually exist.