IaaS supplies data center hardware infrastructures including security and communications.
Normal operating and fixed asset costs are covered. There are serious savings to be had from scale, shared usage, and security expertise.
Numerous option levels are offered which may or may not cover operating systems, networking and firewalls.
Pay for usage billing is common.
Applications are accessed via the application's client/server, browser or Desktop Virtualization
Application usage is accomplished via browser, desktop virtualization, or terminal services from vendors like VMware, Citrix, and Microsoft. Look for Virtual servers and mirrored (duplicate copy) environments. Virtual servers are highly transferable and scalable for rapid growth. When coupled with effective mirroring they reduce disaster recovery to a minor annoyance.
IaaS should be considered when scalability and high performance requirements are important, or where critical internal skill sets are problematic. Web servers are a prime market for this service given the unique communications infrastructure.
PaaS provides IaaS service and layers on the operating system, and various databases, applications, web servers,
and programming languages. Businesses with PaaS can focus on running the business applications
and building light weight software without having to worry about installing, managing, and patching
complicated software stacks and operating systems.
PaaS has been most successful with the rapid evolution of LAMP/WAMP stacks for websites.
In SaaS, the entire application or service is delivered over the web through a browser or screen emulator. Administering users is the most important client input. The hard questions to ask here concern non-renewal and data.