Microsoft today announced a technical preview of Azure Stack. Azure Stack allows an organization to install its own private version of the publicly available Microsoft Azure cloud platform. As with the public cloud offering, Azure Stack offers both infrastructure- and platform-level functionality. As such, Azure Stack can be thought of as a combination or a competitor to both OpenStack and Cloud Foundry.
The real benefit that Azure Stack brings to organizations with an existing Microsoft footprint is that there is no incongruence between their public and private cloud utilization. Where an organization that, for example, takes advantage of Amazon Web Services (AWS) for the public cloud and builds a private cloud on OpenStack might have difficulties in the interplay between its public and private resources, with Azure Stack there is a high fidelity between the public and private offerings.