Microsoft is a keen advocate of the hybrid cloud, or, in other words, an IT infrastructure that has some servers on-premise and some hosted in the public cloud, whether that is Windows Azure or a third-party hosting service.
Its advocacy is not surprising, because it is the obvious way to make sense of a large existing business selling Windows Server and applications such as Exchange and SQL Server, while also meeting the demand for public cloud services.
Nevertheless, the hybrid cloud concept chimes with businesses looking for the scalability and efficiency of cloud-based infrastructure, or taking advantage of the cloud for off-site backup or replication, but without giving up the control and independence that can only be found in your own datacentre.
One reason for Microsoft’s slow start with Azure was its failure to grasp the need for infrastructure as a service (IaaS) alongside platform as a service (PaaS). On its initial release, Azure was an application platform with web roles for web applications, worker roles for background applications, and storage services to persist your data. It used virtual machines (VMs) based on Microsoft’s Hyper-V Hypervisor, but they were stateless, so that, by design, Azure could, at any time, revert a VM to its state at the time you last deployed the application
Even the VM role, introduced later, worked in the same way. This approach has its merits, but meant that Azure could not easily work as an extension of an existing datacentre, but only as a way of running new applications.