Currently, there are two leading solutions: Red Hat OpenShift and Pivotal CF. Both have their pluses and minuses; OpenShift supports the widest swath of languages, but InfoWorld's Andrew Oliver has noted a certain clunkiness in using the product. The "CF" in Pivotal CF stands for the open source Cloud Foundry project, which is gaining popularity, but the fully supported Pivotal CF product runs only on VMware -- again, an expensive proposition.
There are lesser-known solutions, such as Apprenda (which targets .Net), Jelastic (based on Virtuozzo), and CenturyLink AppFog (based on Cloud Foundry). I've also heard good initial reports about IBM BlueMix, also based on Cloud Foundry, but it's still in beta. In short, private PaaS is still very much at an early phase.
The common-denominator benefit of the private cloud is the move to commodity scale-out infrastructure. That sounds fantastic — but it's not what most enterprises have in place. Bending your existing infrastructure to accommodate a vast private cloud, not to mention migrating the lion's share of legacy applications to that cloud, is a losing proposition.
Ultimately, building a private cloud demands replacing old systems with new ones. That can be accomplished step by step, as new initiatives — particularly those supporting customer engagement — demand cloudlike infrastructure. In addition, as legacy systems become too awkward and expensive to maintain, you can replace them with modern cloud solutions.
But even an incremental approach is difficult when, as I've suggested, the private cloud is in such flux. Can anyone tell at this point which private cloud solutions will have the most staying power? Also note that I haven't touched on the subject of SDN (software-defined networking), which is still struggling to deliver solutions enterprise customers can deploy, yet is considered vital to making the most of cloud infrastructure.
The fact is that the major public cloud service providers have solved these problems. That, after all, is their charter as inventors and purveyors of the cloud. Yes, large enterprises that have the resources — not to mention major regulatory compliance constraints — will eventually build their own private clouds. Some already have. And of course, startups that both plan to scale quickly and maintain their own infrastructure tend to commit to cloud architecture from the ground up.
An established enterprise shifting to that paradigm is an altogether different proposition. Theongoing, relentless growth of Amazon Web Services may be the clearest indication that many will continue to avoid the pain, disruption, and expense of building their own clouds and, instead, embrace the public cloud.