Cloud computing is offered in three different service models which each satisfy a unique set of business requirements. These three models are known as Software as a Service (SaaS), Platform as a Service (PaaS), and Infrastructure as a Service (IaaS).
Infrastructure as a Service (IAAS)
Infrastructure as a Service (IAAS) is a form of cloud computing that provides virtualized computing resources over the internet. In an IAAS model, a third party provider hosts hardware, software, servers, storage and other infrastructure components on the behalf of its users. IAAS providers also host users’ applications and handle tasks including system maintenance backup and resiliency planning. IAAS platforms offer highly scalable resources that can be adjusted on-demand which makes it a well-suited for workloads that are temporary, experimental or change unexpectedly. Other characteristics of IAAS environments include the automation of administrative tasks, dynamic scaling, desktop virtualization and policy-based services. Other characteristics of IAAS include the automation of administrative tasks, dynamic scaling, desktop virtualization and policy-based services.
Platform as a Service (PAAS)
Platform as a Service (PAAS) is a cloud computing model that delivers applications over the internet. In a PAAS model, a cloud provider delivers hardware and software tools, usually those needed for application development, to its users as a service. A PAAS provider hosts the hardware and software on its own infrastructure. As a result, PAAS frees users from having to install in-house hardware and software to develop or run a new application. PAAS doesn’t replace a business’ entire infrastructure but instead, a business relies on PAAS providers for key services, such as Java development or application hosting. A PAAS provider, however, supports all the underlying computing and software; users only need to log in and start using the platform-usually through a Web browser interface. PAAS providers then charge for that access on a per-user basis or on a monthly basis.
Software as a Service (SAAS)
Software as a Service(SAAS) is a software distribution model in which applications are hosted by a vendor or service provider and made available to customers over a network, typically the Internet. SAAS has become an increasingly prevalent delivery model as underlying technologies that support Web services and service-oriented architecture (SOA) mature and new development approaches, such as Ajax, become popular. SAAS is closely related to the ASP (Application service provider) and on-demand computing software delivery models. IDC identifies two slightly different delivery models for SAAS namely the hosted application model and the software development model.
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