Cloud Computing 101

Characteristics

Key characteristics of Cloud Computing:
1) On demand
2) Self service enabled
3) Shared resources
4) Pay per use

Service models

There are three different service models in context of cloud computing:

Software as a Service (SaaS)
Consumers use application form service provider running on a cloud infrastructure; all aspects (including infrastructure and application features) are owned and managed by the provider except consumer specific setup/configurations.

Platform as a Service (PaaS)
Service provider owns & manages cloud infrastructure with predefined set of software (e.g. operating system, programming language execution environment, database, web server, libraries, tools etc.) and consumers can build & deploy their applications on the same.

Infrastructure as a Service (IaaS)
Service providers are responsible for providing cloud infrastructure with processing, storage, networks etc. and consumers can use the provisioned resources the way they want to. Consumers can have their choice of operating system, service variant, applications developed in their choice of language and so on.

Deployment models

Cloud computing has four commonly used deployment models as noted below:

• Public cloud (Cloud infrastructure is owned & managed by the service provider and available for open use by general public) 
• Private cloud (Cloud infrastructure is exclusively meant for single organization with multiple business units)
• Community cloud (Cloud infrastructure for specific type of consumers with shared concerns such as government sector, security requirements etc.) and
• Hybrid cloud (Cloud infrastructure which is composition of two or more above mentioned deployment models)