Success is defined as meeting a specified objective. Common objectives are usually: elasticity; flexibility; increased pace and lower TCO. These requirements are in addition to the “must haves” like security and up-time for any production environment.
The first three are easy. The lower TCO is tougher to predictably assure. You have to accurately forecast utilization of various compute resources and compare that to different pricing schemes. But the pricing schemes are so complex that it’s difficult to assure a lower TCO or even know what it will be. It might take less capex but the recurring costs could eat you alive if you’re not careful.
A Private Cloud helps to successfully deliver on the lower TCO promise by providing some degree of predictable pricing in exchange for less elasticity. Often the additional promise of predictable costs is highly desirable and increases the likelihood of meeting the lower TCO requirement. Two things that determine success of a cloud implementation: accurate forecasts of utilization and predictable pricing.