As CIOs develop reference architectures of their functions, processes and data based on the strategy of their business, seasoned Systems Integrators will help them configure their IT environment based on the following conceptual architecture made up of the interconnected 4–tiers.

Dedicated: The dedicated layer suggests a highly secure computing environment, where mission critical tasks will be processed and highly sensitive information will be stored. This represents the true core competency of an organization, leakage of which would give away the competitive advantage, or degradation of performance & reliability of its processing could prove to be catastrophic to the business.
This layer would typically require investment in a dedicated computing platform.

Private Cloud: This layer addresses similar needs as the “Dedicated” layer, and is used for developing, enhancing and testing out mission critical systems as well as carrying out critical research & development work. As such, it needs an environment that is highly secure like the dedicated layer.

Built on the principles of Cloud Computing, this layer will be designed to be readily scalable and sharable between IT systems and applications across the organization.

Shared Environment: A shared environment can be used to address the predictable compute need required to run regularly scheduled applications from inventory management to payroll processing. These systems typically represent a significant portion of the computing needs of an organization.

Important to the operations of a business, these systems can be carried out of an outsourcer’s facility where the computing platform is dedicated for the business but the ancillary processes and resources may be leveraged across multiple clients. Managed through well defined Service Level Agreements, this arrangement proves to be predictable, cost effective, and has in-built innovation from the Systems Integrator.

Public Cloud: Public cloud is an external cloud (like the EC2 and S3) that would be configured to operate as an extension to the computing platform of an organization to handle the spikes in its computing needs.
Due to the open nature of the public cloud, an organization must be able to disaggregate its system and parse out its computing needs into transactions that can be carried out in the external cloud without fear of exposing or losing its critical information.

As governance models and processes make Cloud Computing increasingly secure and user friendly, organizations may feel comfortable moving more and more of their data & processing to it, much like commerce has gradually shifted and become acceptable over the internet. It is envisioned, with time, some of the sensitive tasks processed in the private cloud will gradually be transferred to the public cloud as organizations become more comfortable with the security and governance models of this new computing
platform.