按照美国NIST(国家标准技术研究所)的定义,这个定义也是目前学术界引用比较多的定义,Cloud computing is a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction.
按照这个定义云计算有五个重要特性(On-demand self-service. Broad network access.
Resource pooling. Rapid elasticity. Measured service.),三种服务模式(IaaS, PaaS, SaaS),四种部署模式(私有云private Cloud,公有云public Cloud,社区云community Cloud,混合云hybrid Cloud)。