What if you were able to achieve both efficiency and innovation in all the business domains and applications across your entire portfolio? What if you could take advantage of the cloud and all of its resources and features to get a “the whole is greater than the sum of its parts” effect? With a good roadmap to lead the way, you can. This chapter covers what it means to move your enterprise to the cloud. We’ll provide examples and learning experiences from Microsoft’s own journey, as well as from those of our customers.
In any transformative change, it’s important to understand what the destination is and what the waypoints along the journey will be. There are multiple potential destinations for any application, and
IT cloud deployments will be a mixture of them:
Private cloud In a private cloud, cloud technologies are hosted in an on-premises datacenter. Private clouds can be useful because they can implement a technology stack that is consistent with the public cloud. This might be necessary in scenarios for which certain applications or data cannot be moved off premises. However, private clouds do not provide the cost savings and efficiencies that the public cloud can, because private clouds require a significant capital expense budget and a (potentially large) operations staff.
Infrastructure as a Service (IaaS) In IaaS, the application virtual machines (VMs) are simply moved from on-premises to the cloud. This is the easiest migration strategy and has many benefits, including cost savings. But, it still means that your operations staff will need to perform such tasks as patch management, updates, and upgrades. Nevertheless, IaaS is one of the most common cloud deployment patterns to date because it reduces the time between purchasing and deployment to almost nothing. Additionally, because it is the most similar to how IT operates today, it provides an easy onboarding ramp for the IT culture and processes of today.
Platform as a Service (PaaS) In PaaS, the cloud provider maintains all system software, removing the burden of upgrades and patches from the IT department. PaaS is similar to the traditional three tier model of enterprise software, having a presentation layer (called “Web Role”), a business logic layer (called “Worker Role”), and persistent storage (Microsoft Azure SQL Database or other database). In a PaaS deployment model, all that the enterprise needs to focus on is in deploying its code on the PaaS machines; the cloud provider ensures that operating systems, database software, integration software, and other features are maintained, kept up to date, and achieve a high service level agreement (SLA).
Software as a Service (SaaS) In SaaS, you simply rent an application from a vendor, such as Microsoft Office 365 for email and productivity. This is by far the most cost-effective of all the options because typically the only work involved for the IT department is provisioning users and data and, perhaps, integrating the application with single sign-on (SSO). Typically, SaaS applications are used for functions that are not considered business-differentiating, for which custom or customized applications encode the competitively differentiating business models and rules.
The hybrid cloud Many enterprises might choose to keep some applications on-premises— perhaps they are based on nonstandard systems or out-of-date software, or perhaps they will remain on-premises while waiting for their turn to be migrated to the cloud. In this model, some applications run in the cloud, whereas others remain on-premises, requiring a secure, high-speed communications path between the two environments. In a way, then, the cloud becomes an extension of the existing datacenter, and vice versa.
Source of Information : Microsoft Enterprise Cloud Strategy