Cloud Computing
Overview
Cloud computing is the on-demand availability of computer system resources, especially data storage (cloud storage) and computing power, without direct active management by the user. The term is generally used to describe data centers available to many users over the Internet. Large clouds, predominant today, often have functions distributed over multiple locations from central servers.
History
The history of cloud computing can be traced back to the 1960s, when the concept of an "intergalactic computer network" was introduced by J.C.R. Licklider, who was responsible for enabling the development of ARPANET (Advanced Research Projects Agency Network) in 1969. His vision was for everyone on the globe to be interconnected and accessing programs and data at any site, from anywhere.
Characteristics
Cloud computing exhibits the following key characteristics:
- Agility improves with users' ability to rapidly and inexpensively re-provision technological infrastructure resources.
- Cost reductions are claimed by cloud providers. A public-cloud delivery model converts capital expenditure to operational expenditure.
- Device and location independence enable users to access systems using a web browser regardless of their location or what device they use (e.g., PC, mobile).
- Multi-tenancy enables sharing of resources and costs across a large pool of users thus allowing for:
* Centralization of infrastructure in locations with lower costs (such as real estate, electricity, etc.) * Peak-load capacity increases (users need not engineer and pay for the resources and equipment to meet their highest possible load-levels) * Utilization and efficiency improvements for systems that are often only 10–20% utilized.
Service models
Cloud computing providers offer their services according to several fundamental models: infrastructure as a service (IaaS), platform as a service (PaaS), and software as a service (SaaS). These models are often referred to as the "cloud computing stack" because they build on top of one another.
- Infrastructure as a service (IaaS)
In the most basic cloud-service model, providers of IaaS offer computers – physical or (more often) virtual machines – and other resources.
- Platform as a service (PaaS)
PaaS vendors offer a development environment to application developers. The provider typically develops toolkit and standards for development and channels for distribution and payment.
- Software as a service (SaaS)
In the software as a service (SaaS) model, users gain access to application software and databases. Cloud providers manage the infrastructure and platforms that run the applications.
Deployment models
Private cloud, public cloud, hybrid cloud and multi-cloud are the four main types of cloud computing.
- Private cloud
Private cloud is cloud infrastructure operated solely for a single organization, whether managed internally or by a third party, and hosted either internally or externally.
- Public cloud
A cloud is called a "public cloud" when the services are rendered over a network that is open for public use.
- Hybrid cloud
Hybrid cloud is a composition of two or more clouds (private, community, or public) that remain distinct entities but are bound together, offering the benefits of multiple deployment models.
- Multi-cloud
Multi-cloud is the use of multiple cloud computing and storage services in a single network architecture.