environment. On the other hand, a cloud is hybrid when a  company uses public cloud services for tasks such as prototyping or testing a new application. When the application  is completed it may be moved to the private cloud. In another  situation, the Web servers are on a public cloud service that’s  integrated with payment systems that are run in a private  cloud. A company with a private cloud may choose to combine some  public services for capabilities that are commodities with  private services based on the ability to deliver fast innovation  to their ecosystem. For example, companies are increasingly  discovering that it’s practical to pay a per-user, per-year  price for customer relationship management (CRM) and leave  the day-to-day management to a trusted vendor. But many  companies also want to keep control over some of their most  sensitive data. Therefore, they may choose to keep data about  prospects on a public cloud. However, after those prospects  become customers, the companies may begin storing that  data on their own premises in their own servers, which is the  hybrid cloud model. Regardless of the model that you use, some core capabilities  that are essential in the cloud environment include the areas  covered in this section. A key feature of a cloud environment is that it provides a  platform that’s designed to be elastic (you can use just the  resources you want when you need them), so the users/  customers provision resources, such as computing or storage  resources, that they pay for on a per-unit basis. When the user  no longer needs that resource and stops paying, the resource  is released back into the pool of resources. This helps organizations avoid the cost of idle computing resources.  Instead of purchasing, managing, and maintaining a server  environment, for example, a business can purchase computing  on demand, avoiding capital expenditures. These materials are the copyright of John Wiley & Sons, Inc. and any  dissemination, distribution, or unauthorized use is strictly prohibited. Elasticity and self-service provisioning Core Cloud Capabilities Cloud Services For Dummies, IBM Limited Edition  8