Types of Cloud Computing

Cloud computing is typically classified in two ways:

  1. Type of access to the cloud computing – The working model is referred to as Deployment models
  2. Type of services offered – The working model is referred to as  Service models

Various deployment models :

  1. Public cloud allows systems and services to be easily accessible to the general public. Public cloud may be less secure because of its openness, e.g., e-mail.

    In Public cloud the computing infrastructure is hosted by the cloud vendor at the vendor’s premises. The customer has no visibility and control over where the computing infrastructure is hosted. The computing infrastructure is shared between any organizations.

  2. Private cloud Cloud allows systems and services to be accessible within an organization. It offers increased security because of its private nature.

    The computing infrastructure is dedicated to a particular organization and not shared with other organizations. Some experts consider that private clouds are not real examples of cloud computing. Private clouds are more expensive and more secure when compared to public clouds.

    Private clouds are of two types: On-premise private clouds and externally hosted private clouds. Externally hosted private clouds are also exclusively used by one organization, but are hosted by a third party specializing in cloud infrastructure. Externally hosted private clouds are cheaper than On-premise private clouds.

  3. Community cloud involves sharing of computing infrastructure in between organizations of the same community. It allows systems and services to be accessible by group of organizations.

    For example all Government organizations within the state of California may share computing infrastructure on the cloud to manage data related to citizens residing in California.

  4. Hybrid cloud  is mixture of public and private cloud. However, the critical activities are performed using private cloud while the non-critical activities are performed using public cloud. Organizations may host critical applications on private clouds and applications with relatively less security concerns on the public cloud. The usage of both private and public clouds together is called hybrid cloud. A related term is Cloud Bursting. In Cloud bursting organization use their own computing infrastructure for normal usage, but access the cloud using services like Salesforce cloud computing  for high/peak load requirements. This ensures that a sudden increase in computing requirement is handled gracefully.

Various Service Model:

Service Models are the reference models on which the Cloud Computing is based. These can be categorized into three basic service models as listed below:

  1. Infrastructure As A Service (IAAS)

IaaS provides access to fundamental resources such as physical machines, virtual machines, virtual storage, etc.

  1. Platform As A Service (PAAS)

PaaS provides the runtime environment for applications, development & deployment tools, etc.

  1. Software As A Service (SAAS)

SaaS model allows to use software applications as a service to end users.

The following image shows a comparison between the three types of services:

types_of_service

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