Cloud computing is the delivery of computing as a service rather than a product, whereby shared resources, software, and information are provided to computers and other devices as a utility (like the electricity grid) over a network (typically the Internet).
The concept of cloud computing fills a perpetual need of IT:
- a way to increase capacity or add capabilities on the fly without investing in new infrastructure,
- training new personnel, or licensing new software.
Cloud computing encompasses any subscription-based or pay-per-use service that, in real time over the Internet, extends IT’s existing capabilities.
The term “cloud” is used as a metaphor for the Internet, based on the cloud drawing used in the past to represent the telephone network, and later to depict the Internet in computer network diagrams as an abstraction of the underlying infrastructure it represents.
TYPES OF CLOUD
Public cloud describes cloud computing in the traditional mainstream sense, whereby resources are dynamically provisioned to the general public on a fine-grained, self-service basis over the Internet, via web applications/web services, from an off-site third-party provider who bills on a fine-grained utility computing basis.
Community cloud shares infrastructure between several organizations from a specific community with common concerns (security, compliance, jurisdiction, etc.), whether managed internally or by a third-party and hosted internally or externally. The costs are spread over fewer users than a public cloud (but more than a private cloud), so only some of the benefits of cloud computing are realised.
Hybrid cloud is a composition of two or more clouds (private, community, or public) that remain unique entities but are bound together, offering the benefits of multiple deployment models.
Private cloud is infrastructure operated solely for a single organization, whether managed internally or by a third-party and hosted internally or externally.
They have attracted criticism because users “still have to buy, build, and manage them” and thus do not benefit from lower up-front capital costs and less hands-on management, essentially “[lacking] the economic model that makes cloud computing such an intriguing concept”
Source : Wikipedia.org