The series focusing on cloud essentials for IT professionals includes:

cloud-sunny In Part 1, I talked about what “service” in the context of cloud computing means. Cloud is all about delivering services, i.e. making resources available on demand based on needs, paid by use, and.with the characteristics of ubiquitous network access, resource pooling, etc. Still we need to clearly define what cloud is. Without a common definition for a subject as broad as cloud computing it is hard to navigate through the overwhelming business and technical complexities. So here’s the six million question.

What Is Cloud

It is important to understand that there are services delivery models and deployment models. And both are needed to fully describe what cloud is. There are 3 ways to deliver services via cloud.


or SaaS is a model where an application is available on demand. It is the most common form of cloud computing delivered today. Microsoft Office 365 including: Exchange Online, SharePoint Online, Lync Online and the latest version of Microsoft Office Professional Plus suite is an SaaS offering to businesses.



or PaaS is a platform available on demand for development, testing, deployment and on-going maintenance of applications without the cost of buying the underlying infrastructure and software environments. Windows Azure Platform is a cloud-computing platform on which Microsoft’s internal IT (MSIT) organization has quickly built and deployed the Social eXperience Platform (SXP) to enable social media capabilities across as documented.


image or IaaS is an IT environment with an ability for a subscriber to on demand provision infrastructure. This infrastructure is, for example, delivered with virtual machines in which a subscriber maintains the OS and installed applications, while the underlying fabric is managed by a service provider.

On deployment, there are two base models. Public cloud is cloud computing made available through Internet to the general public or targeted users and is owned by an organization offering cloud services. An example is Microsoft Windows Live as free public cloud offerings for consumers, and Microsoft Online: Office 365 for businesses. Private cloud, on the other hand, is cloud available solely for an organization regardless if the cloud capabilities are managed by the organization or a third party and exists on premise or off premise. Based on the two models, some derive additional models like hybrid cloud, community cloud, etc. to highlight the implementation or intended audiences. For private cloud, two service delivery models: PaaS and IaaS are applicable since in a private setting, one can not deliver SaaS without having PaaS in place. Noticeimageis a solution for building private cloud. Hyper-V Cloud is a set of initiatives, guidelines, and offerings to help emperies deliver IaaS in a managed environment. Also the above mentioned delivery models are significant since once a model is selected to fulfill business objectives, responsibilities are implicitly agreed upon and accepted by the party hosting the cloud facility and the other subscribing the services.

Separation of Responsibilities

An important attribute of Cloud Computing is the separation of a subscriber’s responsibilities from those of a service provider’s. And by subscribing a particular service delivery model, a subscriber in essence agrees to relinquish certain level of access to and control over resources managed by the service provider. As I have discussed in Cloud Computing Primer for IT Pros, we must recognize and be pre-occupied with the limitations of each service delivery model when assessing Cloud. When a particular function or capability like security, traceability, or accountability is needed yet not provided with an intended delivery model, a subscriber needs to either negotiate with the service provider and put specifics in a service level agreement, or employ a different delivery model such that a desired function becomes available. Lack of understanding of the separation of responsibilities in my view frequently results in false expectations of what Cloud Computing can or cannot deliver.

[To Part 1, 2, 3, 4, 5, 6]

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