Cloud Computing

• What is Cloud
•  Enables organization to obtain flexible, secure, and cost-effective IT infrastructure.
  Just pay what you use. No upfront payment charged. Infrastructure can have virtual servers, databases, storage, Messaging etc.
• Service Models.
• IAAS - Infrastructure as service - AWS, Azure
• PAAS - Platform as service - AWS
• SAAS - Software as service - GMAIL (Multi tenant environment) 
• Best value for money

• Essential Characteristics
• On demand self service - Provision computing capabilities, such as server time and network usage, as needed automatically without manual intervention
• Broad network access - Capabilities are available over network and accessed through standard mechanisms that promote use by heterogeneous thin or thick client platforms(eg: mobiles, tablets, laptops and workstations)
• 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 costomer 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. Examples or resources include storage, processing, memory, and network bandwidth
• 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.
• Measured service: Cloud systems automatically control and optimize resource use by leveraging a metering capability 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 consuer of the utilized service.
• Deployment Models(Procurement model for cloud)
• Private cloud: The cloud infrastructure is provisioned for exclusive use by a single organization comprising multiple consumers. It may be owned, managed, and operated by the organization, a thrird party, or some conbination of them, and it may exist on or off premises.
• Community cloud: The cloud infrastructure is provisioned for exclusive use by a specific community of consumers from organizations that have shared concerns. It may be owned, managed, and operated by one or more of the organizations in the community, a thrid 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 exits on the premises of the cloud provider.
• Hybrid cloud: The cloud infrastruture is a composition of two or more distinct cloud infrastrucres(private, community, or public) that remain unique entities, but are bound together by standardized or proprietary technology that enables data and application portability.