• Cloud service providers – cloud service hosters.
  • Heterogeneous cost collection – collection of the cost for any resource that can have a cost assigned to it that resides on a public cloud, private cloud, or traditional IT infrastructure.
  • Hybrid IT – Hybrid IT is an approach to enterprise computing in which an organization provides and manages some information technology (IT) resources in-house but uses cloud-based services for others. A hybrid approach allows an enterprise to maintain a centralized approach to IT governance, while experimenting with cloud computing.

There are three forces driving the adoption of hybrid IT: an enterprise’s need to maintain control of data, the cost effectiveness of cloud components such as software-as-a-service and storage-as-a-service and the desire for an IT department to respond as quickly as possible to rapidly changing business needs.

The term hybrid IT is often used interchangeably with the term hybrid cloud. Hybrid cloud, however, can also refer to a cloud architecture in which a vendor who has a private cloud forms a partnership with a public cloud provider — or a public cloud provider who forms a partnership with a vendor that provides private cloud platforms.

  • 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.
  • 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 standardized or proprietary technology that enables data and application portability (e.g., cloud bursting for load balancing between clouds).
  • Cloud – essential characteristics include:

a) On-demand self-service. A consumer can unilaterally provision computing capabilities, such as server time and network storage, as needed automatically without requiring human interaction with each service provider.

b) Broad network access. Capabilities are available over the network and accessed through standard mechanisms that promote use by heterogeneous thin or thick client platforms (e.g., mobile phones, tablets, laptops, and workstations).

c) Resource pooling. The provider’s computing resources are pooled to serve multiple consumers using a multi-tenant model, with different physical and virtual resources dynamically assigned and reassigned according to consumer demand. There is a sense of location independence in that the customer generally has no control or knowledge over the exact location of the provided resources but may be able to specify location at a higher level of abstraction (e.g., country, state, or datacenter). Examples of resources include storage, processing, memory, and network bandwidth.

d) Rapid elasticity. Capabilities can be elastically provisioned and released, in some cases automatically, to scale rapidly outward and inward commensurate with demand. To the consumer, the capabilities available for provisioning often appear to be unlimited and can be appropriated in any quantity at any time.

e) Measured service. Cloud systems automatically control and optimize resource use by leveraging a metering capability 1 at some level of abstraction appropriate to the type of service (e.g., storage, processing, bandwidth, and active user accounts). Resource usage can be monitored, controlled, and reported, providing transparency for both the provider and consumer of the utilized service.

  • Software as a Service (SaaS) – The capability provided to the consumer is to use the provider’s applications running on a cloud infrastructure 2. The applications are accessible from various client devices through either a thin client interface, such as a web browser (e.g., web-based email), or a program interface. The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, storage, or even individual application capabilities, with the possible exception of limited user-specific application configuration settings.
  • Platform as a Service (PaaS) – The capability provided to the consumer is to deploy onto the cloud infrastructure consumer-created or acquired applications created using programming languages, libraries, services, and tools supported by the provider. The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, or storage, but has control over the deployed applications and possibly configuration settings for the application- hosting environment.
  • Infrastructure as a Service (IaaS) – The capability provided to the consumer is to provision processing, storage, networks, and other fundamental computing resources where the consumer is able to deploy and run arbitrary software, which can include operating systems and applications. The consumer does not manage or control the underlying cloud infrastructure but has control over operating systems, storage, and deployed applications; and possibly limited control of select networking components (e.g., host firewalls).

1. TechTarget:
2. NIST: