Sidebar: Understanding the cloud

As executives other than the CIO begin embracing cloud, the focus becomes more about business strategy and less about technology. However, it’s essential that everyone understand the IT context and the choices available to the business. The figure illustrates cloud’s essential characteristics and outlines key considerations.

Understanding the cloud

Essential characteristics

On-demand self-service

A customer can automatically access computing resources, as needed, without requiring human interaction with the provider.

Broad network access

Services are available over the network and accessed by a variety of computing platforms.

Resource pooling

The provider pools computing resources to serve multiple customers. The resources are dynamically assigned according to demand.

Rapid elasticity

Customers access just what they need, with capabilities quickly scaling up or down.

Measured service

Cloud resource use is automatically managed through metering, enabling customers and providers to monitor, control, and report on usage.

Service model

Software-as-a-service (SaaS)

An application and its supporting environment (hardware, network, operating system, database, etc.) are managed centrally by a service provider. Users typically access the application through a Web browser.

Platform-as-a-service (PaaS)

This model enables companies to build custom cloud-based applications. Everything but the specific application code is hosted remotely by a service provider—hardware, network, operating system, and database.

Infrastructure-as-a-service (IaaS)

Hardware and network resources are available on-demand from the service provider, while the customer manages any applications and their operating systems in-house.

Deployment model

A business will consider whether its internal IT organization or a technology vendor will host and manage the cloud deployment and which model is appropriate.


The hardware and software that compose the service are maintained for the use of a single organization, which might have distinct business units or internal customers.


The service—and its underlying hardware and software—are shared by multiple organizations or customers.


In this model, a company augments its private cloud with public-based cloud services when needed.