云计算定义

"Cloud computing is a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources (for example, networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction."

• US National Institute of Standards and Technology

This definition is the most widely quoted and used version globally. Many countries and industries have adopted it, and this is the highly recommended starting point for your organization's working definition for the cloud. This definition is so important that we should take a few minutes to review it in detail.

Cloud computing is a model. It is not a specific technology. You cannot go and buy a cloud computer. The term is used to describe an economic and operational model for the provisioning and consumption of IT infrastructure and associated services. The term can also be extended to cover both business and public-sector mission models. What do these models enable? Why cloud?

They enable ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources. Universal, convenient, on-demand network access means from anywhere and at any time. The network may include the global public internet, but it may also refer to a global private network. The concepts of ubiquitous, convenient, and on-demand take the viewpoint of the cloud service provider's intended users. Shared pool means that the individual user or organization does not pay for all the resources in the pool. The end user pays only for what they use when they use it. This concept is the heart of the cloud computing economic model. If you need to pay for the resource even when you are not using it, you are not leveraging the cloud computing economic model. Configurable means that the service capability can be changed essentially in real time to meet a specific user's requirements.

That final phrase, "...can be rapidly provisioned and released with minimal management effort or service provider interaction," implies a high degree of automation. Cloud service providers operate a highly automated, services-oriented platform that requires relatively few people. Automation is enabled through brutal establishment and enforcement of rigorous IT standards. Automation also enables self service, so if a prospective service provider cannot offer their capabilities without human interaction, you should be worried.