2. Cloud Computing
   
2. Cloud Computing
Cloud computing leverages the efficient pooling of on-demand, self-managed virtual infrastructures, which are consumed as services. The following figure illustrates key cloud computing principles and service layers.
Figure 1. Cloud Computing Layers
 
The National Institute of Standards and Technology (NIST) specifies three service layers in a cloud. VMware defines the following service layers:
*Software as a Service (SaaS) – Business-focused services presented directly to users in a service catalog.
*Platform as a Service (PaaS) – Technology-focused services for application development and deployment presented directly to application developers through a service catalog.
*Infrastructure as a Service (IaaS) – Infrastructure containers for better agility, automation, delivery of components, and related purposes.
Additional service layers are expected to become available as other services, such as Desktop as a Service, are developed.
Companies adopt cloud computing to improve quality of service, business agility, and operating cost efficiency.
*Quality of service – Standardized and automated service offerings, with associated availability levels and Service Management, help to promote quality of service. Customers can provision a reliable vCloud service with predictable service levels to get the service they need, as they need it, within expected timeframes. To provide standardized, repeatable service, IT must introduce operational efficiencies and control the underlying infrastructure and applications.
*Business agility – A proactive, service-driven model helps IT to provide and manage services, which are added to a service catalog to facilitate end-user self-service. IT retains control of the environment; for example, by protecting against over-subscription. Providing the reliable, dynamic services expected from a vCloud requires automation of complex, time-consuming, error-prone tasks. This model reduces IT lag, improving business agility and increasing speed to market.
*Increased cost efficiency – The key to increased cost efficiency is reduction of operational expenses. The current operational cost and burden of managing IT—approximately 70% operational expenses (OpEx) and 30% capital expenses (CapEx)—must change, especially as IT becomes more service-driven. IT operational processes for vCloud computing must be enhanced by automation and the use of tools for management, compliance, and process governance. IT organizational structures must be optimized to support vCloud operations and management.