Private cloud – The cloud infrastructure is provisioned for exclusive use by a single organization comprising
Multiple consumers (e.g., business units). It may be owned, managed, and operated by the organization, a third party, or some combination of them, and it may exist on or off premises.
Community cloud – The cloud infrastructure is provisioned for exclusive use by a specific community of consumers from organizations that have shared concerns (e.g., mission, security requirements, policy,
and compliance considerations). It may be owned, managed, and operated by one or more of the organizations in the community, a third party, or some combination of them, and it may exist on or off premises.
Public cloud – The cloud infrastructure is provisioned for open use by the general public. It may be
owned, managed, and operated by a business, academic, or government organization, or some combination of them. It exists on the premises of the cloud provider.
Hybrid cloud – The cloud infrastructure is a composition of two or more distinct cloud infrastructures (private, community, or public) that remain unique entities, but are bound together by standardised or proprietary technology that enables data and application portability (e.g., cloud bursting for load balancing between clouds).
This area is one of the most interesting areas in IT at the moment. There is so much work in this area and a shortage of resources. In order to be able to play any one of many roles, from implementation and architecture, to core sales for vendors, a rich portfolio of skills is required. There are main vendors whose technologies have spawned the definition and use cases for Cloud computing and Cloud Enablement. These include VMware, EMC, Cisco, Netapp, Microsoft, IBM, HP, Dell, Rackspace, NASA, to name but a small number.
This has lead to differing and sometimes non-compatible architectures and associated ecosystems, that all constitute ‘Cloud’ in varying degrees to internationally accepted standards as to what defines ‘Cloud’ and its various ‘Service Models’ such as the aforementioned NIST explanation.
There are many viable IaaS offerings in the Public Cloud Space from the likes of Google Compute Engine, HP Cloud, and Microsoft Windows Azure. These three vendors launched their offerings in the past year, but they are behind the undisputed leader Amazon Web Services and also Rackspace both from a functional maturity perspective and also percentage of market share.
On the private cloud front we see there is a predominant battle for construction of IaaS coming by default from the flavour of virtualisation vendor used by the enterprise/corporation/ISP/SI/SO/government body/finance house in question. It is this that determines how successful any attempt at IaaS cloud ‘Hybridisation’ will be for those parties and the ability to ‘burst’ and consume resources from a compatible ecosystem provider. It is heavily open to personal opinion as to what successful means in the eyes of architects and the SOA/TOGAF et al methods used when planning the solutions in question.