Delivery Models

 3.4 Deployment Models 

There are four deployment models in cloud computing which encompass how infrastructure is set up. The four models include public, private, hybrid and community clouds. Figure 2 below is a graphical representation of which deployment method will most likely be used for workloads.



A Public Cloud is a pay-per-use service made available to the public in general. Public clouds are viewed by organizations as a way to save costs and time without obligations of deployment and maintenance because the public cloud infrastructure is shared with a larger network of organizations [3,7,10].

For organizations that require unshared networks or a very secure network an option would be the use of a Private Cloud. This type of cloud is not available to the public because it is an internal datacenter of the organization. Therefore, accessibility and data are only for internal users. However, an external supplier may provide or manage the private cloud on or off premises. In this case, the infrastructure is solely operated for a specific consumer [3,7,10].

Hybrid Clouds  are a combination of private and public clouds. In a hybrid cloud, the public cloud component handles non-critical information, whereas, in the private cloud component, business-critical services and data are kept. The delivery models of the public and private cloud remain unique [3,7,10].

Community Clouds  are the most recent clouds. Community clouds are used and controlled by a group of organizations that share interests, such as a common mission or specific security requirements. The community cloud may start as a private cloud from individual researchers and as the infrastructure is shared between organizations it grows into a community cloud on or off premise [3,7,10].

<p class="MsoNormal"><span style="font-size:12.0pt;line-height:107%;font-family: "Arial",sans-serif">To visualize cloud computing, we take an example from Chen, et.al., where their “Reference Model for Cloud (RMC) is an Enterprise Cloud Architecture for industrial practices and plays a central role in defining a research cloud as the one below” [6].

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<p class="MsoNormal"><span style="font-size:12.0pt;line-height:107%;font-family: "Arial",sans-serif"> <span style="font-size:12.0pt;line-height:107%; font-family:"Arial",sans-serif;mso-fareast-font-family:Calibri;mso-ansi-language: EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">Chen et al., uses tower architecture to describe cloud computing. The virtualization level lies on top of the hardware level. The hardware level supports reliable cloud services. There are three core levels made up of Infrastructure-as-a-Service, IaaS, Platform-as-a-Service, PaaS and Software-as-a-Service, SaaS. IaaS is an infrastructure for self-providing, managing and controlling virtualization of the resources. PaaS is used as a platform to develop, build, design and deploy cloud services and applications. IaaS is the first layer of the cloud and provides specific applications to the end user. Each layer of the cloud is under strict security to ensure features including single sign-on, auditing, and access control and identity management.

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