In this chapter, the authors consider cloud computing as a core topic and various models emerging around it such as its services and delivery models, its economic aspects, applications, usages, challenges, and so on. Cloud computing covers a range of delivery and service models. In this chapter, cloud service delivery models (i.e., Software-as-a-Service, Platform-as-a-Service and Infrastructure-as-a-Service) and cloud deployment models (private cloud, community cloud, public cloud, and hybrid cloud) are described. The right service delivery and deployment option have to be chosen for an organization’s cloud application, according to organizational needs.
Top1. Introduction
Traditional software applications are based on a model with large and upfront licensing costs in addition to annual support costs. An enterprise software package requires software/hardware deployment, configuration, servers, backup and network provisioning to support the number of users mentioned in license agreement. In addition, software applications are highly customizable, which comes at a cost. These notes are about the traditional software model which were applicable when there were no cloud. Instead, the term cloud computing refers “to both the applications delivered as services over the Internet and the hardware and systems software in the datacenters that provide those services.” (Armbrust et al., 2009)
Cloud computing covers a wide range of delivery and service models. The common characteristics of these service models are pay-as-you-go, on-demand, outsourced, elasticity, and reliability. In conjunction with the growth of cloud computing new approaches to distributed computing and data analysis are also emerging. The aim of this chapter is to explore the current service delivery models and deployment options in cloud computing.
A public cloud is a cloud infrastructure made available to the public users in a pay-as-you-go model (Armbrust et al., 2009). In such a model, the service being sold is utility computing. Current examples of public utility computing include Amazon Web Services (AWS), Google App Engine, and Microsoft Azure. Instead, the term private cloud refers to internal data centers of a business or an organization that are not made available to the public.
Public cloud or private cloud terms refer to the deployment model of a cloud. A private cloud operates for a single organization, but can be managed on-premise or off-premise. On the other hand, a public cloud has an infrastructure that is available to the general public or a large industry group and is likely owned by a cloud based company.
On the other side, the services have long been referred to as Software as a Service (SaaS). The data center hardware and software is what we will call a cloud. Thus, generally speaking cloud computing is the sum of SaaS and utility computing, but does not normally include private clouds. We will generally use cloud computing, replacing it with one of the other terms only when clarity demands it.
To start the opening perspective of this chapter, a comparison between cloud services of Amazon and Google is illustrated in Figure 1.
Figure 1. Google versus Amazon cloud services
2. SERVICE DELIVERY
Cloud offerings are typically categorized as Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS). The distinction between the service models is based on the service abstraction layer to the end user, e.g., hardware, development environment, system software, etc. The end user then has complete control over the software stack above the abstracted level. Thus, in IaaS a virtual machine or hardware is provided to the end user; the user controls the operating system and the entire software stack. We describe each of these service models and present existing examples in the commercial cloud space to understand their characteristics.
Currently, there are three main service delivery models in cloud computing: i.e. Software-as-a-Service, Infrastructure-as-a-Service, and Platform-as-a-Service. In Figure 2, a comparison between these three service delivery models are demonstrated. Figure 2 shows which parts of a cloud could be managed by a user based on the service delivery model.
Figure 2. Cloud service delivery models
SaaS provides the ability to use the software in a cloud environment, such as Web-based email or Customer Relationship Management (CRM) for the consumer.
PaaS is a variation of SaaS whereby the development environment is offered as a service. It provides the consumer the ability to deploy applications through a programming language or tools supported by the cloud platform provider. An example of platform as a service is an Eclipse/Java programming platform provided with no manual tasks or no downloads required.
IaaS provides infrastructure such as compute instances, network bandwidth, and storage so that people can run any software or operating system.
Figure 3 illustrates Oracle cloud services based on service delivery models.
Figure 3. Oracle cloud architecture: Service delivery models perspective. Used with permission.