What Is Cloud Computing?

Cloud computing delivers IT as a service. It might be your own private cloud accessible only within your organization, the public cloud of an external provider or a hybrid cloud that spans both.

Features of a cloud include:

• Virtually unlimited processing and storage capacity
• Abstracted, pooled resources
• Elasticity (the ability to scale up or down easily)
• On-demand, self-service provisioning
• High level of automation
• Consumption-based billing

Cloud Service Models
There are three cloud service models:

• Software as a Service (SaaS) gives your users web access to applications hosted on a service provider's infrastructure. A wide range of applications can be delivered through a SaaS model, such as customer relationship management, collaboration, email and enterprise resource management.
• Platform as a Service (PaaS) is a software development and hosting environment made up of development tools, databases, middleware and infrastructure software.
• Infrastructure as a Service (IaaS) enables your system administrators and developers to self-provision the compute, storage and network resources they need to deploy and run applications and operating systems.

Cloud Structures
There are three primary deployment models for cloud services:

• Private clouds, whether operated and hosted by your enterprise IT department or by an external provider, are for the exclusive use of your organization.
• Public clouds are open to any number of organizations and individual users on a shared basis. Using a public cloud minimizes your initial capital investment and combines agility and efficiency with massive scalability.
• Hybrid clouds link private and public clouds, providing access to extra resources when the private cloud hits maximum utilization. Or, a hybrid cloud might split computing by tier between private and public clouds. For example, the database may reside in the private cloud while the application server is located in the public cloud.

With any of these structures, cloud computing enables an application to take advantage of idle or excess compute, storage and network capacity that is shared with other applications. The cloud is one of the keys to avoiding overprovisioning and enabling efficient load balancing among your computing resources.