Cloud computing services provide a virtualized computing infrastructure (referred to as the "cloud") from which businesses and individuals can access resources such as storage, computing, or applications over a network from anywhere in the world on demand. The cloud consists of a pool of computing resources such as networks, servers, storage, applications, and services that are provided through a pay-per-use model.

Characteristics

Cloud computing services are characterized by several primary attributes:

• On-demand self-service: Users can access cloud resources on an as-needed basis, automatically and immediately.
• Broad network access: Cloud resources are available to a wide variety of client platforms in any location over a network.
• Resource pooling and elasticity: Cloud resources are provisioned to rapidly respond to multiple users, meeting consumer demand in any location, in any quantity, at any time.
• Measured service: Transparency to the user and provider is offered by monitoring and reporting of resource usage statistics. Cloud services are often priced on a pay-per-use or subscription basis.

Service Models

There are a number of cloud computing service models:

• Infrastructure as a service (IaaS): Processing, storage, network, and other computing resources are provided to the consumer for on-demand provisioning of servers running operating system or application software.
• Platform as a service (PaaS): Consumers can create and deploy custom applications developed with programming languages, libraries, and tools supported by the provider.
• Software as a service (SaaS): Users have access to software applications running on cloud infrastructure through a web portal or program interface.

In each of the service models, the consumer does not need to manage the underlying cloud infrastructure, but may have control over configuration settings for operating systems, storage, and applications.

Deployment Models

There are a variety of deployment models for cloud computing services:

• Private cloud: Cloud infrastructure serves a single organization. Cloud hardware and software may be managed and hosted either internally or by a third party.
• Community cloud: Cloud services are rendered to a collection of organizations with common concerns, with infrastructure owned and managed by one more of the organizations or third parties.
• Public cloud: The cloud services provider owns and manages cloud infrastructure to provide services over an open network for a public audience.
• Hybrid cloud: Cloud infrastructure is a composition of two or more cloud deployment models (private, community, or public) that are unique entities bound together by common technology that allows data portability.

References

Amazon Web Services—What is Cloud Computing?

Cloud Computing: Principles and Paradigms. New York, USA: Wiley Press. pp. 1-44.

National Institute of Standards and Technology—The NIST Definition of Cloud Computing

Voorsluys, William; Broberg, James; Buyya, Rajkumar (February 2011)—Introduction to Cloud Computing [pdf]

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NCS Pearson, Inc. | The cloudPLUS