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C lo u d C o m p u t i n g


Pros &Cons A

ccording to the National Institute of Standards and Technology (NIST), cloud computing is a model for enabling on-demand access to a pool of computing resources that can be provisioned and released with minimal effort. Furthermore, NIST categorises cloud computing into three service models: Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS). Each has distinct advantages and disadvantages that impact the information technology (IT) efforts of an enterprise as well as its business practices and finances. As the CIO’s role evolves from pure IT service provider toward full partner in defining and executing enterprise strategies, you'll find yourself navigating those pros and cons of cloud computing.

The Service Models The spectrum of cloud computing service models ranges from IaaS to PaaS to SaaS, with subtle variations in between. These models can be understood according to the increasing levels of IT services that each provides, along with the concomitant increasing levels of control that the enterprise must relinquish to the cloud provider. IaaS providers deliver virtual server environments to the enterprise, upon which the IT department deploys all of the software layers it chooses. PaaS providers deliver similar virtual server environments, but preloaded with specific operating systems, database systems, and development environments, thus decreasing the amount of effort needed by the IT department in setting up and maintaining those layers, but restricting the environments’ use to development and deployment upon those layers. SaaS providers deliver fully functional applications that are accessed by end users via thin clients like web browsers; they do not expose the underlying layers to the customers. The spectrum of cloud computing service models offers an increasing collection of managed IT services with concomitant decreasing control and flexibility. The three cloud computing service models all provide varying lev-


cto forum 21 November 2011

The Chief Technology Officer Forum

The cloud computing service models have their own issues with regard to systems integration among the various on-premise and cloud systems that are deployed. By Alexander Pasik

els of economies of scale, impose varying degrees of vendor lock-in, and have their own issues with regard to systems integration among the various on-premise and cloud systems that are deployed. Furthermore, the suitability of cloud computing varies with regard to IT and business maturity. The value proposition for IT has always been economies of scale. IT enabled the growth of businesses by allowing for massive transaction speeds and volumes. In computing’s early years, the expense associated with data centers resulted in time-sharing -- a few businesses investing in mainframes, and others buying processing and storage from them. Microprocessors and storage in the 1980s resulted in a backlash against centralised data centers; since hardware was so cheap, why not localise IT and ignore any savings from reuse? However, by the 1990s it was clear that despite low-cost processing and storage, IT costs escalated dramatically due to the management and maintenance associated with highly distributed, unshared, and underleveraged resources. Cloud computing represents a return to time-sharing, but leveraging the advances of the last 30 years. All of the service models enable some economies of scale. In IaaS, the data center (real estate, power, cooling), the processing and storage hardware, and the firewalls and networks, are all shared among the cloud provider’s clients. Fixed costs are distributed, resulting in savings that can be shared among

Fair Weather Cloud  

It is no longer about whether to go for the cloud or not. The question CIOs are asking themselves is when and for what when and for what | P...

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