Cloud computing often referred as the cloud, the practice of using a network of remote servers to store, manage, and process data, rather than a local server or computer.
Via cloud model the user can easily get a convenient web access to computing resources (for example, servers, storage devices, data networks, applications and services - both together and separately) that can be promptly provided and released with minimal operating costs, paid to the cloud computing provider.
The National Institute of Standards and Technology (NIST) recorded the following mandatory characteristics of cloud computing:
Self-service on demand - the consumer independently identifies and changes computing needs, such as server time, access and processing speeds, the amount of stored data without interacting with a representative of the service provider;
Universal access over the network - services are available to consumers over the data network, regardless of the device used;
Resource pooling - a service provider integrates resources to serve a large number of consumers in a single pool for dynamic redistribution of capacity between consumers in a constantly changing demand; while consumers control only the basic parameters of the service (for example, data volume, access speed), but the actual distribution of resources provided to the consumer is performed by the supplier ;
Elasticity - services can be provided, expanded, narrowed at any time, without additional costs for interaction with the supplier, usually in automatic mode;
Consumption accounting - the service provider automatically calculates the consumed resources at a certain level of abstraction (for example, the amount of data stored, the bandwidth, the number of users, the number of transactions) and, based on this data, estimates the volume of services provided to consumers.
Private cloud is an infrastructure intended for use by one organization, including several consumers (for example, units of the same organization), possibly also customers and contractors of this organization. A private cloud can be owned, managed and operated by both the organization itself and a third party (or some combination thereof), and it can physically exist both inside and outside the owner's jurisdiction.
The public cloud is an infrastructure designed for free use by the general public. A public cloud can be owned, managed and operated by commercial, scientific and government organizations (or some combination thereof). A public cloud exists physically in the jurisdiction of the owner-provider of services.
The community cloud is a kind of infrastructure intended for use by a specific community of consumers from organizations that have common tasks (for example, security requirements, policies, missions, and compliance with different requirements). A public cloud may be co-operative (co-owned), managed and operated by one or more community organizations or a third party (or any combination thereof), and it can physically exist both inside and outside the owner's jurisdiction.
A hybrid cloud is a combination of two or more different cloud infrastructures (private, public or community) that remain unique objects but are linked together by standardized or proprietary data and application technologies (for example, short-term use of public cloud resources for load balancing between clouds).