SPI is an acronym for the most common cloud computing service models, Software as a Service, Platform as a Service and Infrastructure as a Service.
1 – Software as a Service (SaaS) : Software as a Service (SaaS) cloud implementation delivers software or, more generally described, an application to its end user. SaaS enables a service provider to make applications available over the Internet. This capability eliminates the need to install software on users’ computers, and it can be helpful for mobile or transient workforces.
SaaS Benefits :
Inexpensive: Little or no capital investment
Flexible: Offered as an on-demand service; customize your contract
Stable: SaaS applications are installed on reputed, protected, and redundant hardware
Rapid deployment: Little to no time to provision and deploy
Accessible: Only thing needed is internet access
2 – Platform as a Service (PaaS) : Platform as a Service (PaaS) is the platform that delivers a solution stack as a service. It supports in deployment of applications. It does not involve the cost and complexity of buying and managing the underlying hardware and software and even the provisioning hosting capabilities. It provides all the facilities that are required to support the complete life cycle of building and delivering web applications and services, which are completely accessible from the Internet.
3 – Infrastructure as a Service (IaaS) : Infrastructure as a Service (IaaS) enables users to rent equipment and run a data center. In an IaaS arrangement, clients are typically billed based on the resources they consume, much like a utility company bills one for the amount of electricity one uses. Examples of IaaS include Rackspace’s CloudServers offering, in which a client rents a virtual server running an operating system of his/her choice. He/she then installs the applications according to the requirement onto that virtual server. Major examples of IaaS are: Amazon Elastic Compute Cloud (EC2), Eucalyptus, GoGrid, FlexiScale, Linode, RackSpace Cloud, Terremark.