Cloud Computing Explained!

Cloud computing is a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources. The types of computing resources can include networks, servers, data storage, applications and services. These computing resources can be rapidly provisioned and released with minimal management effort or service provider interaction.

Cloud computing is to use the optimum amount of computing resources that one needs from a shared pool of computing resources.

Given the resources are shared, the users of cloud computing will not have access to dedicated resources. However, given the ability to rapidly provision, when the demand for computing needs for a particular user is high, lager portion of the pool could be acquired by that user. And when the demand lowers, the resources could be released back to the pool. The principle is to use optimum amount of resources at all times, that meets the needs of a user. The convenience of this model is made possible by the automated provisioning and releasing of resources. Automation eliminates the need for manual interaction both on the part of the user as well as the service provider. It is an obvious assumption that the pool of resources is sufficiently large that simultaneous high demand from multiple users could be catered by the pool of resources made available by the service provider.

Rapid provisioning and releasing of resources to scale up and down based on demand ensures operational efficiencies for a user in cloud computing.

There are three delivery models in cloud computing

1. Infrastructure as a Service (IaaS)
   Basic computing resources such as processing power, data storage and networking components are provided to the consumers.  The consumer have access to control the operating system, storage, deployed applications and possibly networking components such as firewalls and load balancers. However, the cloud infrastructure beneath them, that is used to provision virtual machine instances or storage instances are not exposed to the consumer and would be managed by the service provider.
2. Platform as a Service (PaaS)
   Application hosting environments are provided to the consumer. The environment provided can be used by the consumer as the platform on top of which consumer controlled applications are run. The platform is typically an application framework. The platform environment and the infrastructure on top of which it is run (operating system, hardware and network infrastructure) will be managed by the service provider on behalf of the consumer. 
3. Software as a Service (SaaS)
   Application software are provided to the consumer. All three layers - application, platform and infrastructure are managed by the service provider on behalf of the consumer. The consumer can just focus on the use of the application.

There are three deployment models in cloud computing.

1. Public Cloud
   Public cloud services are characterized as being available to clients from a third party service provider via the Internet. The term “public” here reflects the availability over the internet. “Public” does not necessarily mean free, and there could be free cloud computing services as well as paid services. 
   Public cloud vendors typically provide an access control mechanism for their users so that, users will have isolation from other users when using the shared computing resources. Thus, public clouds have the ability to ensure data security and privacy for the users.
   Public clouds often provide an elastic, cost effective means to deploy solutions, to leverage the provisioning and releasing characteristics of the shared computing resources pool.
   
2. Private Cloud
   In a private cloud, the pool of resources are owned and managed by an organization for its internal users. Data and processes can be managed within the organization without the restrictions of network bandwidth, security exposures and legal requirements that may apply when using a public cloud.
   Private cloud offers many of the benefits of a public cloud computing environment, such as being elastic and service based. In addition, given that the networks used are restricted and designated, private cloud services can offer the users greater control of the cloud, encouraging them to deploy sensitive applications and data with greater trust on levels of security and resilience.
   
3. Hybrid Cloud
   A hybrid cloud is a combination of a public cloud and private cloud that facilitates the interoperability of the applications deployed on both clouds. The rationale is to reap the best benefits from both flavors. 
   In this model users typically deploy non-sensitive applications and data to the public cloud, while keeping sensitive services and data in their control in the private cloud.

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