Cloud computing offers a variety of trends for businesses to increase their IT capacity without having to add infrastructure, personnel, and software. Cloud computing providers offer their services based on three models such as Software as a service (SaaS), Platform as a service (PaaS), and infrastructure as a service (IaaS). Among this IaaS is the most basic model.
Infrastructure as a Service(IAAS) involves services related to hardware that includes disk storage and virtual servers. Amazon EC2, Amazon S3, Rack space Cloud Servers and Flexiscale are some of the leading sellers of IaaS. It allows an organization to run and process entire data center application stacks, from the operating system up to the application, on a service provider’s infrastructure. Amazon’s Elastic Compute Cloud is perhaps the most famous public cloud infrastructure available.
In this cloud service model, the cloud providers offer computers – as physical or often as virtual machines such as raw storage, firewalls, load balances, and networks. On demand, these resources are supplied by the IaaS providers from their large pools installed in data centers. Local area networks including IP addresses are part of the offer. For a wide area connectivity, the Internet can be used.
Here the cloud users will install operating system images and application software on their machines and also they are responsible for patching and maintaining the operating systems and application software. For this, cloud providers will typically bill based on the amount of resources allocated and consumed.
We can say that IaaS Cloud is a platform through which businesses can use equipment in the form of hardware, servers, storage space etc. at pay-per-use service.
Software as a service (SAAS) is the most common form of cloud computing. Cloud offers complete software to the users and they are accessed based pay per use basis. Saleforce.com’s CRM, Google apps, Gmail and Hot-mail are prime examples of SAAS.
In this model, cloud providers install and operate application software in the cloud and cloud users access these software from cloud clients. Here the cloud users do not manage the cloud infrastructure and platform on which the application is running.
In ‘Platform as a service’ (PaaS), cloud offers computing platform and solution stack services. In this model, cloud providers present a computing platform and/or solution stack which includes operating system, environment for executing programming language, database, and web server. Application developers can develop and run their software solutions on a cloud platform without the cost and buying and managing the underlying hardware and software layers. Or PaaS provides a platform on which a customer can run its own applications.