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Cloud Computing – Types available


Cloud computing is where software applications, data storage and processing capacity is accessed over the Internet. To explain how this works in practice, we are going to examine three ways to cloud compute. The three building blocks of cloud computing are software-as-a-service or SaaS, platform-as-a-service or PaaS and infrastructure-as-a-service or IaaS. All these allow users to run applications and store data online. However, each offers a different level of user flexibility and control. In basic terms, SaaS allows users to run existing online applications. PaaS allows users to create their own cloud applications using supply-specific tools and languages and IaaS allows users to run any applications they please on Cloud hardware of their own choice.


Okay, that might right now still be as clear as stagnant pond water! So let’s work through again in more detail. Software-as-a-service or SaaS is the easiest way to cloud computer, where off-the-shelf applications are accessed over the Internet. For example, Google, Microsoft and Zoho each offer the online word processor, spreadsheet and presentation package. There are also some great creative SaaS tools including Pixar, Jaycut and Aviary as well as dedicated business applications from Employease, Netsuite and Salesforce.


The advantage of SaaS is that all applications are free or charged on a subscription basis. SaaS applications are also accessible to any computer on the Internet and are excellent to collaborative working. This said, in business there are many situations where generic application will not suffice.


Platform-as-a-service or PaaS provide an environment and a set of tools that allow users to create their own new online applications. For example, Google has a product called App Engine that enables anybody to develop, run and maintain their own web applications on Google’s infrastructure. Microsoft also has a PaaS offering called Azure that allows users to develop and run Windows applications in Microsoft’s region of the cloud. Salesforce is also a big player on the PaaS landscape with an offering called force. com. Both Google App Engine and force.com also currently allow one application to be built and hosted for free.


All PaaS applications allow users to create new online applications very rapidly at low cost. Such applications may also be used privately within just one business or made available publicly. This said adopting PaaS is restricted technically as it limits developers to the programming languages and other tools, but that PaaS provider has on offer. There is also the risk of vendor lock-in as applications built on one providers platform cannot be moved to another.


Infrastructure-as-a-service or IaaS allows a business to run whatever applications it requires on a supplier’s cloud hardware. This means that existing applications can be migrated from a company’s Data Centre in order to reduce IT costs. The fundamental unit of cloud infrastructure is the server; today service can also be physical or virtual. Physical servers are discrete individual computers; in contrast the so termed virtual server instances are software controlled slices of real physical servers that are shared amongst many users via a process called virtualization.


Depending on the types of servers involved IaaS comes in four categories; firstly there is the most secure and costly option of private cloud, which is when a specific number of physical servers are dedicated to one customer. Secondly, we have dedicated hosting where a customer rents physical servers on demand with the cost and the number of servers always matching their requirements. Thirdly, there is hybrid hosting where a mix of physical servers and virtual server instances are rented on demand in an effort to reduce a cost and further increase flexibility. Finally, we have cloud hosting when a customer rents virtual server instances on demand and often on the hourly basis.


Several companies are now operating in the IaaS marketplace; for example, Amazon offers a number of cloud hosting products that offer a variety of virtual server instances to be purchased by the hour. These can be launched in minutes using an Amazon machine image or IMI configured either to customer specification or containing software from Oracle, Sun, IBM or other suppliers. Alternative IaaS providers include Rackspace who offer all hosting categories from a private cloud to cloud hosting and go good to offer cloud hosting, hybrid hosting and dedicated hosting solutions.


Anybody wanting to do cloud computing has to get to grips with its fundamental building blocks of software-as-a-Service, platform-as-a-service and infrastructure-as-a-service.