Cloud computing is the convergence and evolution of several concepts from virtualization, distributed application design, grid and enterprise IT management to enable a more flexible approach for deploying and scaling applications.

Cloud promises real costs savings and agility to customers. Traditionally, once an application was deployed it was bound to a particular infrastructure, until the infrastructure was upgraded. The result was low efficiency, utilization and flexibility. Clouds allow applications to be dynamically deployed onto the most suitable infrastructure at run time.

IT departments and infrastructure providers are under increasing pressure to provide computing infrastructure at the lowest possible cost. In order to do this, the concepts of resource pooling, virtualization, dynamic provisioning, utility and commodity computing must be leveraged to create a public or private cloud that meets these needs.

Evolution of IT Architecture
In  the 1980s and 1990s, with the shrinking costs of networking and computing infrastructure, client/server provided the ability to split the application tier away from the server tier. In recent years, as data centres started to fill out and power, space and cooling became more expensive, concepts such as commodity grid computing and virtualization started to become established. Cloud computing takes these concepts further by allowing self-service, metered usage and more automated dynamic resource and workload management practices.

Building Blocks of the Cloud
The building blocks of cloud computing are rooted in hardware and software architectures that enable  innovative infrastructure scaling and virtualization. However, the next infrastructure innovations are around more dynamic provisioning and management in larger clusters both within an external to the conventional corporate data centre.

Virtualized Infrastructure: It provides the necessary abstraction to ensure that an application or business service is not directly tied to the underlying hardware infrastructure such servers, storage or networks. This allows business services to move dynamically across virtualized infrastructure resources in a very efficient manner.

Virtualized Applications: Applications are decoupled from the underlying hardware, operating system, storage and network to enable flexibility in deployment. Virtualized application servers that can take advantage of  grid execution coupled with SOA enable the greatest degree of scalability to meet the business requirements.

Enterprise Management: It provides top-down, end-to-end management of the virtualised infrastructure and applications for business solutions. The enterprise management layer handles the full lifecycle of virtualized resources and provides additional common infrastructure elements for service level management, metered usage, policy management, license management, and disaster recovery.

Security and Identity Management: Clouds must leverage a unified identity and security infrastructure to enable flexible provisioning, yet enforce security policies throughout. As clouds provision resources outside the enterprise’s legal boundaries, it becomes essential to implement an Information Asset Management system to provide the necessary controls to ensure sensitive information is protected and meets compliance requirements.

Development Tools: Next generation development tools can leverage cloud’s distributed computing capabilities. These tools not only facilitate service orchestration but also enable business processes to be developed that can harness the parallel processing capabilities available to clouds.

Diverse Options for Enterprises
Cloud computing is typically divided into three levels of service offerings: Software as a Service (SaaS), Platform as a Service (PaaS), and Infrastructure as a service (IaaS). These levels support virtualization and management of  differing levels of  the solution stack.

Software as a Service: A SaaS provider typically hosts and manages a given application in their own data centre and makes it available to multiple tenants and users over the Web. Some SaaS providers run on another cloud provider’s PaaS or IaaS service offerings.

Platform as a Service: PaaS is an application development and deployment platform delivered as a service to developers over the Web. This platform consists of infrastructure software, and typically includes a database, middleware and development tools. A virtualized and clustered grid computing architecture is often the basis for this infrastructure software. Some PaaS offerings have a specific programming language or API.

Infrastructure as a Service: IaaS is the delivery of hardware and associated software as a service. It is an evolution of  traditional hosting that does not require any long term commitment and allows users to provision resources on demand. Amazon Web Services Elastic Compute Cloud (EC2) and Secure Storage Service are examples of IaaS offerings.

Architecture Implications and Principles
To take full advantage of the benefits of cloud computing,there are a number of  architectural implications that should be observed.

Application Architecture: Application services should abstract resource allocation and avoid the tight binding of its resources to invokers of the service. To take advantage of the cloud’s scalability capabilities, applications should take advantage of distributed application design and utilize multi threading wherever possible.

Information Architecture: Cloud computing offers the potential to utilize information anywhere in the cloud. This increases the complexity associated with meeting legal and regulatory requirements for sensitive information. Employing an Information Asset Management system provides the necessary controls to ensure sensitive information is protected and meets compliance requirements.

Technology Architecture: Implementing Service Oriented Architectures (SOA) provides the most effective means of leveraging the capabilities of cloud computing. SOAs distributed nature, service encapsulation; defined service level objectives, virtualized interfaces, and adherence to open standards align with architectural requirements.

Implementing Cloud Computing
As we focus on building the cloud, a number of models have been developed for deploying a cloud infrastructure.

Private Clouds: In a private cloud, the infrastructure for implementing the cloud is controlled completely by the enterprise. Typically, private clouds are implemented in the enterprise’s data centre and managed by internal resources.

Public Clouds: In a public cloud, external organisations provide the infrastructure and management required to implement the cloud. Public clouds dramatically simplify implementation and are typically billed based on usage. This transfers the cost from a capital expenditure to an operational expense and can quickly scale to meet the organisation’s needs.

Hybrid Clouds: To meet the benefits of both approaches, newer execution models have been developed to combine public and private clouds into a unified solution. Applications with significant legal, regulatory or service level concerns for information can be directed to a private cloud.  

Conclusion
Markets are developing for delivery of software applications, platforms, and infrastructure as a service to IT departments over the “cloud”. These services are readily accessible on a pay-peruse basis and offer great alternatives to businesses that need the flexibility to rent infrastructure on a temporary basis or to reduce capital costs. Oracle’s complete, open, and integrated product set offers a compelling value proposition at each level of  the design and our certified Oracle Enterprise Architects can help customers discover a cloud roadmap that works for them.