A cloud deployment model defines where the physical servers are deployed and who manages them. There are key differences between public, hybrid and private cloud deployments.
The National Institute of Standards and Technology (NIST) defines a private cloud deployment in which the ". . . infrastructure is operated solely for an organization."
Private cloud deployments give users immediate access to computing resources hosted within an organization's infrastructure and the resources are dedicated solely for that organization's use. Users self-provision and scale collections of resources drawn from the private cloud, typically via web service interface, just as with a public cloud. However, because a private cloud deployment is always within the organization's existing data center—and behind the organization's firewall—a private cloud deployment is subject to the organization's physical, electronic, and procedural security measures and thus offers a higher degree of security over sensitive code and data.
With a private cloud deployment, the performance of physical hardware can be controlled and maintained by the organization, and can thus markedly improve data center efficiency while reducing operational expense.
NIST defines a public cloud deployment in which "(t)he cloud infrastructure is made available to the general public . . . and is owned by an organization selling cloud services."
Public clouds offer computing resources for the general public over the Internet but the resources are owned by the organization selling the computing services. The public cloud service vendor allows customers to self-provision resources, typically via a web service interface. Customers use resources as needed on a pay-as-you-go basis. Public clouds offer access to large pools of scalable resources on a temporary basis without the need for capital investment in data center infrastructure.
With public cloud, infrastructure costs are shared across customers, which result in economies of scale. Data control might be an issue depending on a number of factors, including the type and sensitivity of the data as well as the industry and local laws concerning the data. In some situations, a hybrid or private cloud deployment may be required.
Finally, NIST states that a hybrid cloud deployment typically tries to maximize the benefits of both public and private clouds. A company will have two or more unique clouds available, but these clouds ". . . are bound together by . . . technology that enables data and application portability (e.g., cloud bursting for load balancing between clouds)."
Hybrid clouds combine one or more public clouds and one or more private clouds by technology that enables data and application migration between them. Hybrid clouds typically use a shared API to enable hybrid operation.
With hybrid cloud, organizations can utilize the cost benefits of a public cloud and when needed, protect confidential data in a private cloud deployment.
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