Cloud computing providers harness large economies of

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Cloud computing providers harness large economies of scale through resources pooling. They put together a vast network of servers and hard drives and apply the same set of configurations, protection and the works for them. Virtualization:Users do not have to care about the physical states of their hardware nor worry about hardware compatibility. Elasticity:Addition of more hard disk space or server bandwidth can be done with just a few clicks of the mouse on-demand. Geographical scalability is also available in cloud computing - one can choose to replicate data to several data centres around the world. Automatic/easy resource deployment: The user only needs to choose the types and specifications of the resources he require and the cloud computing provider will configure and set them up automatically. Metered billing:Users are charged for only what they use. These principles allow cloud computing to bring more cost-savings, automation and flexibility to the users, compared to using a traditional web service provider. 1.3Types of Cloud Computing Providers There are three kinds of cloud computing providers - Infrastructure as a Service (IaaS), Platform as a Service (PaaS) and Software as a Service (SaaS).
Ch1: Cloud Computing Figure 1 - The XaaS pyramid[iii]IaaS providers offer hardware and the bare minimum software for users to develop on e.g. virtual servers, hard disk space. Users have broad control over the services offered by IaaS providers as they are able to configure settings to a very large extent and they are free to implement and utilize any form of software and programming environment on top of the services. An example of an IaaS provider is Rackspace (see Figure 2). Figure 2- Rackspace is an IaaS that allows users to start up a server and operating system of their choice[iv] For services offered by PaaS providers, users have very little control over their software and programming environment. This is because PaaS providers implement a software layer over the hardware they offer, forcing users to work with the providers' software layer. This is not necessarily a bad thing as PaaS providers reduce the technical expertise needed for users to create their own web application. An example of a PaaS provider is Google App Engine (see Figure 3). One can make use of Google App Engine to host an application on the web and make use of the database and file storage services provided by Google App Engine to complement their application. However, As Google App Engine is a PaaS, only Java and Python can be used to code the application.
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Software Development Tools and Technologies Figure 3 - Google App Engine comes with a server, database and file storage[v]SaaS providers basically offer software for users over the Internet through a web browser. An example of a SaaS is Google Docs, where one can edit documents through the software delivered over the Internet. The main advantage of using a SaaS is that you do not have to worry about

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