A cloud is used to describe a data cloud. On demand – usually via the Internet and device-independent – shared computer resources can be provided quickly and with little effort as a service, for example in the form of servers, data storage or applications, and billed according to use.
The offer and use of these computer resources is defined and usually takes place via an application programming interface (API) or, for users, via a website or app.
The five necessary criteria that a cloud must meet are:
Selbstbedienung auf Abruf
Services can be provided on demand without human interaction (self-service).
Broad network access
Services are accessible via the network with standard mechanisms that enable use with end devices such as notebooks, smartphones, tablets or workstations.
Ressource pooling
Services are accessible via the network with standard mechanisms that enable use with end devices such as notebooks, smartphones, tablets or workstations. Therefore, the user usually has no control over which computer resources are used to provide the service (e.g., on which server or with which database).
Rapid elasticity
Power can be adaptively provisioned and released to scale up and down as needed, in some cases automatically. From the user’s point of view, the available computer resources seem unlimited and services can be adjusted at any time in any amount.
Measured service Cloud-Systeme
Systems control with the help of measurable numbers and optimize computer resources, which are collected depending on the respective performance. This refers to memory, bandwidth or active user accounts. To be able to ensure transparency for the user as well as for the provider, the usage of the service can be monitored, controlled and provided as a report.
Defined by the National Institute of Standards and Technology, USA