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Cloud Services with Windows Azure : Cloud Computing 101

4/7/2011 4:08:14 PM
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Just like service-oriented computing, cloud computing is a term that represents many diverse perspectives and technologies. In this book, our focus is on cloud computing in relation to SOA and Windows Azure.

Cloud computing enables the delivery of scalable and available capabilities by leveraging dynamic and on-demand infrastructure. By leveraging these modern service technology advances and various pervasive Internet technologies, the “cloud” represents an abstraction of services and resources, such that the underlying complexities of the technical implementations are encapsulated and transparent from users and consumer programs interacting with the cloud.

At the most fundamental level, cloud computing impacts two aspects of how people interact with technologies today:

  • how services are consumed

  • how services are delivered

Although cloud computing was originally, and still often is, associated with Web-based applications that can be accessed by end-users via various devices, it is also very much about applications and services themselves being consumers of cloud-based services. This fundamental change is a result of the transformation brought about by the adoption of SOA and Web-based industry standards, allowing for service-oriented and Web-based resources to become universally accessible on the Internet as on-demand services.

One example has been an approach whereby programmatic access to popular functions on Web properties is provided by simplifying efforts at integrating public-facing services and resource-based interactions, often via RESTful interfaces. This was also termed “Web-oriented architecture” or “WOA,” and was considered a subset of SOA. Architectural views such as this assisted in establishing the Web-as-a-platform concept, and helped shed light on the increasing inter-connected potential of the Web as a massive collection (or cloud) of ready-to-use and always-available capabilities.

This view can fundamentally change the way services are designed and constructed, as we reuse not only someone else’s code and data, but also their infrastructure resources, and leverage them as part of our own service implementations. We do not need to understand the inner workings and technical details of these services; Service Abstraction , as a principle, is applied to its fullest extent by hiding implementation details behind clouds.


With regards to service delivery, we are focused on the actual design, development, and implementation of cloud-based services. Let’s begin by establishing high-level characteristics that a cloud computing environment can include:

  • generally accessible

  • always available and highly reliable

  • elastic and scalable

  • abstract and modular resources

  • service-oriented

  • self-service management and simplified provisioning

Fundamental topics regarding service delivery pertain to the cloud deployment model used to provide the hosting environment and the service delivery model that represents the functional nature of a given cloud-based service. The next two sections explore these two types of models.

Cloud Deployment Models

There are three primary cloud deployment models. Each can exhibit the previously listed characteristics; their differences lie primarily in the scope and access of published cloud services, as they are made available to service consumers.

Let’s briefly discuss these deployment models individually.

Public Cloud

Also known as external cloud or multi-tenant cloud, this model essentially represents a cloud environment that is openly accessible. It generally provides an IT infrastructure in a third-party physical data center that can be utilized to deliver services without having to be concerned with the underlying technical complexities.

Essential characteristics of a public cloud typically include:

  • homogeneous infrastructure

  • common policies

  • shared resources and multi-tenant

  • leased or rented infrastructure; operational expenditure cost model

  • economies of scale and elastic scalability

Note that public clouds can host individual services or collections of services, allow for the deployment of service compositions, and even entire service inventories.

Private Cloud

Also referred to as internal cloud or on-premise cloud, a private cloud intentionally limits access to its resources to service consumers that belong to the same organization that owns the cloud. In other words, the infrastructure that is managed and operated for one organization only, primarily to maintain a consistent level of control over security, privacy, and governance.

Essential characteristics of a private cloud typically include:

  • heterogeneous infrastructure

  • customized and tailored policies

  • dedicated resources

  • in-house infrastructure (capital expenditure cost model)

  • end-to-end control

Community Cloud

This deployment model typically refers to special-purpose cloud computing environments shared and managed by a number of related organizations participating in a common domain or vertical market.

Other Deployment Models

There are variations of the previously discussed deployment models that are also worth noting. The hybrid cloud, for example, refers to a model comprised of both private and public cloud environments. The dedicated cloud (also known as the hosted cloud or virtual private cloud) represents cloud computing environments hosted and managed off-premise or in public cloud environments, but dedicated resources are provisioned solely for an organization’s private use.

The Intercloud (Cloud of Clouds)

The intercloud is not as much a deployment model as it is a concept based on the aggregation of deployed clouds (Figure 1). Just like the Internet, which is a network of networks; intercloud refers to an inter-connected global cloud of clouds. Also like the World Wide Web, intercloud represents a massive collection of services that organizations can explore and consume.

Figure 1. Examples of how vendors establish a commercial intercloud.


From a services consumption perspective, we can look at the intercloud as an on-demand SOA environment where useful services managed by other organizations can be leveraged and composed. In other words, services that are outside of an organization’s own boundaries and operated and managed by others can become a part of the aggregate portfolio of services of those same organizations.

Deployment Models and Windows Azure

Windows Azure exists in a public cloud. Windows Azure itself is not made available as a packaged software product for organizations to deploy into their own IT enterprises. However, Windows Azure-related features and extensions exist in Microsoft’s on-premise software products, and are collectively part of Microsoft’s private cloud strategy. It is important to understand that even though the software infrastructure that runs Microsoft’s public cloud and private clouds are different, layers that matter to end-user organizations, such as management, security, integration, data, and application are increasingly consistent across private and public cloud environments.

Service Delivery Models

Many different types of services can be delivered in the various cloud deployment environments. Essentially, any IT resource or function can eventually be made available as a service. Although cloud-based ecosystems allow for a wide range of service delivery models, three have become most prominent:

Infrastructure-as-a-Service (IaaS)

This service delivery model represents a modern form of utility computing and outsourced managed hosting. IaaS environments manage and provision fundamental computing resources (networking, storage, virtualized servers, etc.). This allows consumers to deploy and manage assets on leased or rented server instances, while the service providers own and govern the underlying infrastructure.

Platform-as-a-Service (PaaS)

The PaaS model refers to an environment that provisions application platform resources to enable direct deployment of application-level assets (code, data, configurations, policies, etc.). This type of service generally operates at a higher abstraction level so that users manage and control the assets they deploy into these environments. With this arrangement, service providers maintain and govern the application environments, server instances, as well as the underlying infrastructure.

Software-as-a-Service (SaaS)

Hosted software applications or multi-tenant application services that end-users consume directly correspond to the SaaS delivery model. Consumers typically only have control over how they use the cloud-based service, while service providers maintain and govern the software, data, and underlying infrastructure.

Other Delivery Models

Cloud computing is not limited to the aforementioned delivery models. Security, governance, business process management, integration, complex event processing, information and data repository processing, collaborative processes—all can be exposed as services and consumed and utilized to create other services.

Note

Cloud deployment models and service delivery models are covered in more detail in the upcoming book SOA & Cloud Computing as part of the Prentice Hall Service-Oriented Computing Series from Thomas Erl. This book will also introduce several new design patterns related to cloud-based service, composition, and platform design.


IaaS vs. PaaS

In the context of SOA and developing cloud-based services with Windows Azure. Figure 2 illustrates a helpful comparison that contrasts some primary differences. Basically, IaaS represents a separate environment to host the same assets that were traditionally hosted on-premise, whereas PaaS represents environments that can be leveraged to build and host next-generation service-oriented solutions.

Figure 2. Common differentiations between delivery models.

We interact with PaaS at a higher abstraction level than with IaaS. This means we manage less of the infrastructure and assume simplified administration responsibilities. But at the same time, we have less control over this type of environment.

IaaS provides a similar infrastructure to traditional on-premise environments, but we may need to assume the responsibility to re-architect an application in order to effectively leverage platform service clouds. In the end, PaaS will generally achieve a higher level of scalability and reliability for hosted services.

Other -----------------
- SOA with .NET and Windows Azure : Orchestration Patterns with WF - Compensating Service Transaction
- SOA with .NET and Windows Azure : Orchestration Patterns with WF - State Repository
- SOA with .NET and Windows Azure : Orchestration Patterns with WF - Process Centralization
- SOA with .NET and Windows Azure : Process Abstraction and Orchestrated Task Services (part 4) - Publishing WF Workflows as REST Services
- SOA with .NET and Windows Azure : Process Abstraction and Orchestrated Task Services (part 3)
- SOA with .NET and Windows Azure : Process Abstraction and Orchestrated Task Services (part 2)
- SOA with .NET and Windows Azure : Process Abstraction and Orchestrated Task Services (part 1) - Workflows Published as ASMX Services
- Service-Orientation with .NET : Service Composition and Orchestration Basics - Orchestration (part 2)
- Service-Orientation with .NET : Service Composition and Orchestration Basics - Orchestration (part 1)
- SOA with .NET and Windows Azure : Service Composition 101 (part 2)
 
 
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