In Computer Networking, Cloud Computing is a phrase used to describe a variety of computing concepts that involve a large number of computers connected through a communication network such as the Internet. It is very similar to the concept of utility computing.
In science, Cloud Computing is a synonym for distributed computing over a network, and means the ability to run a program or application on many connected computers at the same time.
The phrase is often used in reference to network-based services, which appear to be provided by real server hardware, and are in fact served up by virtual hardware, simulated by software running on one or more real machines.
Such virtual servers do not physically exist and can therefore be moved around and scaled up or down on the fly without affecting the end user, somewhat like a cloud becoming larger or smaller without being a physical object.
In common usage, the term "the cloud" is essentially a metaphor for the Internet. Marketers have further popularized the phrase "in the cloud" to refer to software, platforms and infrastructure that are sold "as a service", i.e. remotely through the Internet. Typically, the seller has actual energy-consuming servers which host products and services from a remote location, so end-users don't have to; they can simply log on to the network without installing anything. The major models of cloud computing service are known as software as a service, platform as a service, and infrastructure as a service. These cloud services may be offered in a public, private or hybrid network. Google, Amazon, Oracle Cloud, Salesforce, Zoho and Microsoft Azure are some well-known cloud vendors.
Cloud Computing relies on sharing of resources to achieve coherence and economies of scale, similar to a utility (like the electricity grid) over a network. At the foundation of cloud computing is the broader concept of converged infrastructure and shared services.
The cloud also focuses on maximizing the effectiveness of the shared resources. Cloud resources are usually not only shared by multiple users but are also dynamically reallocated per demand. This can work for allocating resources to users.
For example, a cloud computer facility that serves European users during European business hours with a specific application (e.g., email) may reallocate the same resources to serve North American users during North America's business hours with a different application (e.g., a web server). This approach should maximize the use of computing powers thus reducing environmental damage as well since less power, air conditioning, rackspace, etc. is required for a variety of functions. With cloud computing, multiple users can access a single server to retrieve and update their data without purchasing licenses for different applications.
The term "moving to cloud" also refers to an organization moving away from a traditional CAPEX model (buy the dedicated hardware and depreciate it over a period of time) to the OPEX model (use a shared cloud infrastructure and pay as one uses it).
Proponents claim that cloud computing allows companies to avoid upfront infrastructure costs, and focus on projects that differentiate their businesses instead of infrastructure. Proponents also claim that cloud computing allows enterprises to get their applications up and running faster, with improved manageability and less maintenance, and enables IT to more rapidly adjust resources to meet fluctuating and unpredictable business demand. Cloud providers typically use a "pay as you go model." This can lead to unexpectedly high charges if administrators do not adapt to the cloud pricing model.
The term "cloud computing" is mostly used to sell hosted services in the sense of application service provisioning that run client server software at a remote location. Such services are given popular acronyms like 'SaaS' (software as a service), 'PaaS' (platform as a service), 'IaaS' (infrastructure as a service), 'HaaS' (hardware as a service) and finally 'EaaS' (everything as a service).
End users access cloud-based applications through a web browser, thin client or mobile app while the business software and user's data are stored on servers at a remote location. Examples include Amazon web services and Google App engine which allocate space for a user to deploy and manage software "in the cloud".
The development of the Internet from being document centric via semantic data towards more and more services was described as "dynamic web". This contribution focused in particular in the need for better meta-data able to describe not only implementation details but also conceptual details of model-based applications.
The present availability of high-capacity networks, low-cost computers and storage devices as well as the widespread adoption of hardware virtualization, service-oriented architecture, autonomic, and utility computing have led to a growth in cloud computing.
The origin of the term cloud computing is unclear, although it is often attributed to the Internet Systems Division of Compaq Computer (George Favaloro, Philip Reagan, Jeff Whatcott, Ken Evans, Ricardo Cidale, and others). The expression cloud is commonly used in science to describe a large agglomeration of objects that visually appear from a distance as a cloud and describes any set of things whose details are not inspected further in a given context.
Meteorology: a weather cloud is an agglomeration.
Mathematics: a large number of points in a coordinate system in mathematics is seen as a point cloud;
Astronomy: a cloud of gas and particulate matter in space is known as a nebula (Latin for mist or cloud),
Physics: The indeterminate position of electrons around an atomic kernel appears like a cloud to a distant observer
Cloud Computing is the result of evolution and adoption of existing technologies and paradigms. The goal of cloud computing is to allow users to take beneﬁt from all of these technologies, without the need for deep knowledge about or expertise with each one of them.
The cloud aims to cut costs, and help the users focus on their core business instead of being impeded by IT obstacles.
The main enabling technology for cloud computing is virtualization. Virtualization generalizes the physical infrastructure, which is the most rigid component, and makes it available as a soft component that is easy to use and manage. By doing so, virtualization provides the agility required to speed up IT operations, and reduces cost by increasing infrastructure utilization. On the other hand, autonomic computing automates the process through which the user can provision resources on-demand. By minimizing user involvement, automation speeds up the process and reduces the possibility of human errors.
Users face difficult business problems every day. Cloud computing adopts concepts from Service-oriented Architecture (SOA) that can help the user break these problems into services that can be integrated to provide a solution. Cloud computing provides all of its resources as services, and makes use of the well-established standards and best practices gained in the domain of SOA to allow global and easy access to cloud services in a standardized way.
Cloud computing also leverages concepts from utility computing in order to provide metrics for the services used. Such metrics are at the core of the public cloud pay-per-use models. In addition, measured services are an essential part of the feedback loop in autonomic computing, allowing services to scale on-demand and to perform automatic failure recovery.
Cloud Computing is a kind of grid computing; it has evolved by addressing the QoS (quality of service) and reliability problems. Cloud computing provides the tools and technologies to build data/compute intensive parallel applications with much more affordable prices compared to traditional parallel computing techniques.
Cloud Computing shares characteristics with:
Client–server model: Client–server computing refers broadly to any distributed application that distinguishes between service providers (servers) and service requestors (clients).
Grid computing: "A form of distributed and parallel computing, whereby a 'super and virtual computer' is composed of a cluster of networked, loosely coupled computers acting in concert to perform very large tasks."
Mainframe computer: Powerful computers used mainly by large organizations for critical applications, typically bulk data processing such as: census; industry and consumer statistics; police and secret intelligence services; enterprise resource planning; and financial transaction processing.
Utility computing: The "packaging of computing resources, such as computation and storage, as a metered service similar to a traditional public utility, such as electricity."
Peer-to-peer: A distributed architecture without the need for central coordination. Participants are both suppliers and consumers of resources (in contrast to the traditional client–server model).
Cloud gaming: Also known as on-demand gaming, is a way of delivering games to computers. Gaming data is stored in the provider's server, so that gaming is independent of client computers used to play the game. One such current example, would be a service by OnLive which allows users a certain space to save game data, and load games within the OnLive server.
In analogy to above usage the word cloud was used as a metaphor for the Internet and a standardized cloud-like shape was used to denote a network on telephony schematics and later to depict the Internet in computer network diagrams. The cloud symbol was used to represent the Internet as early as 1994, in which servers were then shown connected to, but external to, the cloud.
References to Cloud Computing in its modern sense can be found as early as 1996, with the earliest known mention to be found in a Compaq internal document. The term became popular after Amazon.com introduced the Elastic Compute Cloud in 2006.