Private Cloud
First we consider the Private Cloud. The NIST definition is: 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. Private clouds are a choice for companies that already own datacenter and developed IT infrastructure and have particular needs around security or performance. They are a better choice for the company datacenter than Legacy servers in so many ways, bringing many benefits derived from virtualization and automation. However they also provide Challenges and disadvantages, mostly in that the enterprise needs to migrate or re-factor applications to take advantage of the Cloud automation.
Public Cloud
Now let us consider the Public Cloud. The NIST definition is: 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 and is a form of providing public cloud services and a Cloud Service Providers business model Brings economy of scale in pooling datacenter resources, virtualization and on-demand provisioning Allows outsourcing enterprise IT infrastructure Solves/addresses disaster recovery problem Suitable for SME and agile companies. However, the Data and processing environment are not under control of enterprises, which for applications or data with a security requirement may raise concerns. Furthermore, Service Providers can’t be perfect, power outages, network issues, and so on can disrupt service. Although the security and reliability of the public cloud will almost certainly exceed that of the private cloud due to the skill and staff size of the public cloud operator versus the enterprise itself, it is not 100% fail safe. Their SLA will certainly be problematic for many enterprises.
Hybrid Cloud
The NIST definition for Hybrid Cloud is: 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 standardized or proprietary technology that enables data and application portability (e.g., cloud bursting for load balancing between clouds). Hybrid cloud, while the most complicated configuration to manage, is also the most economical model for modern companies. It combines core cloud based enterprise infrastructure and high load tasks outsourcing to public clouds. It also Combines benefits of the controlled environment in private clouds and rapid elasticity of public clouds However, it requires deeper enterprise IT/cloud modernization. Processes/workflow require re-engineering and re-architecting. And the challenges of getting seamless integration between the Private and the Public cloud can be solved but by custom work, and the issues of Compatibility, standardization and compliance are not turnkey yet.
Community Cloud
The Community Cloud, while used by several constituencies, is something slightly different from a Public Cloud, The NIST definition is – 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. The Community Cloud then involves cooperation and integration of IT infrastructure and resources from multiple organizations. It May serve large inter-organizational projects. For example, the scientists form many organizations at the CERN Large Hadron Collider (HC)
