Three service models of cloud computing: IaaS, PaaS and SaaS
Infrastructure (infrastructure)-as-a-Service, Platform (platform)-as-a-Service, Software (software)-as-a-Service. The infrastructure is at the bottom, the platform is in the middle, and the software is at the top.
IaaS: Infrastructure-as-a-Service is the first layer.
PaaS: Platform-as-a-Service (Platform as a Service) The second layer is the so-called PaaS, sometimes called middleware.
SaaS: Software-as-a-Service is the third layer.
At the bottom, infrastructure as a service - IaaS
IaaS packages computing platforms such as servers with storage and network resources through virtualization technology, and provides them to users in the form of API interfaces. Users no longer need to rent a computer room or maintain servers and switches themselves. They only need to purchase IaaS services to obtain these resources.
Above IaaS, Platform as a Service - PaaS
PaaS is built on top of IaaS, and provides the operating environment for business software in addition to the infrastructure. The "virtual host" often used in personal websites actually belongs to the category of PaaS. "Virtual Host" address, "Virtual Host" will automatically run these codes to generate corresponding Web pages. In addition to forming the environment in which the software itself runs, PaaS usually also has corresponding storage interfaces. These resources can be called directly through FTP and other methods, and users do not need to initialize the bare disk from scratch.
The top layer, software as a service - SaaS
SaaS is the most mature and well-known type of cloud computing service, and software-as-a-service itself was a very popular concept before cloud computing really became hot. The goal of SaaS is to put the back-end environment in which everything runs on the cloud and deliver services directly to end users through a thin client—usually a web browser. End users request services from the cloud on demand without maintaining any infrastructure or software operating environment locally. The difference between SaaS and PaaS is that it is not the developers of the software that use SaaS, but the end users of the software.