Web content that relies on interactivity, social networking and personalization is becoming the dominant form, but it puts particular demands on the network, since it requires a low-latency environment that can provide sites that respond quickly to user input. Content delivery networks (CDNs), which are designed to deliver large amounts of static content, may be too slow to provide this environment. Even public clouds may not be adequate: They provide a generic network that cannot be tuned to the demands of a particular application. Outages are also a problem.
So if your company has a cloud application with a predictable audience size or one that is costing you more than $25,000 a month to host, you may want to consider maintaining a private cloud. It is important to remember that using a private cloud does not preclude also using the public cloud. There is a spectrum of possibilities, including using a hybrid solution.
This paper is an overview of the factors that decision makers who are developing a public-to-private cloud-migration strategy should consider, recognizing that the public versus private cloud strategy is not an all-or-nothing proposition. There is considerable flexibility along a spectrum of implementation choices. The paper describes some pitfalls that must be avoided along the way, and it provides a case study of Zynga, a company that has found a way to use both the private and public clouds to create a hybrid solution.