Cloud Computing - An Introduction

Cloud Computing:

 Cloud Computing is a technology, which provides computation, software, data access and storage services, without requiring the client/end-user knowledge of the physical location and configuration of the system that delivers the service.

Types of cloud computing:

  Cloud Computing can be classified into 4 types based on hosting.

Public Cloud: 

•  Computing infrastructure is hosted at the vendor’s premises. 
•  The customer has no visibility over the location of the cloud computing infrastructure.
•  The computing infrastructure is shared between organizations.

Private Cloud:  

•  Computing architecture is dedicated to the customer and is not shared with other organisations.
•  They are expensive and are considered more secure than Public Clouds.
•  Private clouds may be externally hosted ones as well as in premise hosted clouds.

Hybrid Cloud: 

•  Organisations host some critical, secure applications in private clouds. 
•  The not so critical applications are hosted in the public cloud.
•  The combination is known as Hybrid Cloud.
•  Cloud bursting is the term used to define a system where the organisation uses its own infrastructure for normal usage, but cloud is used for peak loads.

Community Cloud:

•  The cloud infrastructure is shared between the organizations of the same community.
•  For example, all the government agencies in a city can share the same cloud but not the non government agencies.

Classification of Cloud:

On the basis of service, there are three types available in cloud computing.

Infrastructure as a Service(IAAS): 

Hardware related services are provided using the principles of Cloud Computing. These include disk storage and virtual servers. Amazon EC2, Amazon S3, Rackspace Cloud Servers are some of the leading vendors.

Platform as a service(PAAS): 

Development platforms are provided on the cloud. The platforms may not be compatible with each other. Wikipedia puts it appropriately as “‘Platform as a service’ (PaaS) the delivery of a computing platform and solution stack as a service.PaaS offerings facilitate deployment of applications without the cost and complexity of buying and managing the underlying hardware and software and provisioning hosting capabilities, providing all of the facilities required to support the complete life cycle of building and delivering web applications and services entirely available from the Internet.PaaS offerings may include facilities for application design, application development, testing, deployment and hosting as well as application services such as team collaboration, web service integration and marshalling, database integration, security, scalability, storage, persistence, state management, application versioning, application instrumentation and developer community facilitation. These services may be provisioned as an integrated solution over the web.“ Google App Engine, Microsoft Azure and Saleforce’s force.com are the leaders in this category. 

Software as a service (SAAS): 

This is the most common form of cloud computing which we see in action. It is a complete software offering on the cloud. They are accessed by the customers on pay per use basis. Saleforce.com’s CRM, Google apps  etc are the prime example of such a service. Salesforce.com’s CRM, Gmail and Hotmail are prime examples of SAAS.