Private clouds. The Cloud infrastructure is operated solely for an organization. It may be managed by the organization or a third party and may exist on premise or off premise. This indicates that private cloud is established for a specific group or organization and limits access to just that group. It operates dedicatedly for a single organization. Private cloud infrastructure may be set-up On- premise or off-premise and may be managed either internally or by third-party service providers. Private clouds offer highest level of security and control but are expensive. A private cloud is built for the exclusive use of one customer, who owns and fully controls this cloud. Additionally, there are variations of this in terms of ownership, operation and so on. The fact that the cloud is used by a specific customer is the distinguishing feature of any private cloud. A private cloud might be owned by the customer, but built, installed, and managed by a third party rather than the customer. The physical servers might be located at the customer‘s premises or sited in a collocation facility. A recently introduced alternative to a private cloud is a virtual private cloud. In a virtual private cloud, a customer is allocated a private cloud within the physical infrastructure of a public cloud. Due to the allocation of specific resources within the cloud the customer can be assured that their data stored on and processing is done only on dedicated servers (i.e., these servers are not shared with any other customer of the cloud provider). An example would be the NASA‘s Nebula Private Cloud which is an infrastructure-as-a-service implementation for scientific data and Web based applications [10].
