Cloud computing is a disruptive model for enabling on-demand, convenient, flexible access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be quickly provisioned and released with minimal management effort or service provider interaction.
This cloud model is composed of five essential characteristics, three service models, and four deployment models as per NIST.
On-demand self-service: Use credit card and enjoy the resources (Virtual machine, Storage, Database) from public cloud without any interaction to service providers or any delay due to workflows/permissions. It takes less than a MINUTE!!! And believe me, you are not day dreaming…It’s a reality; Go to http://aws.amazon.com/ and verify!!!
Real world example: SMS activation:
Prerequisite: Enough balance in the Mobile (Map it with Credit Card in Cloud Model)
Request Service by calling on *110# (Airtel) (Map it with http://aws.amazon.com/ in Cloud Model)
And you can easily use the resources.
Balance/Usage: with *123*3# you know the available amount of SMS (In case of Cloud, All Cloud Service Provider gives Dashboard/ Management Console/ Cost Control Dashboard which gives you information regarding your resource usage, cost and many more things.
Broad network access: Resources are available over network and can be accessed via Smartphones, iPads, mobile phones, tablets, laptops, and workstations.
Real world example: Videos on Mobile Web
The way we use Applications, wallpapers and ringtones from Internet…Those are resources used…
The more suitable example can be the way we watch videos over internet; similarly we can use various resources on Cloud as well…
Resource pooling: A resource pool is a resource set which is homogeneous with respect to some activity. The Cloud Service 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.
Real world example: As we all know, in software engineering, a connection pool is a cache of database connections maintained so that the connections can be reused when future requests to the database are required.
Purpose: to enhance the performance of executing commands on a database.
In case of Cloud Resources are pooled together and its capacities are used in unified manner to enhance the performance.
Rapid elasticity: Application can expand and contract on demand, across all its tiers (presentation layer, services, database, security…). This also implies that application components can grow independently from each other. So if you need more storage for your database, you should be able to grow that tier without affecting, reconfiguring or changing the other tiers.
Real world example: In physics, elasticity (or stretchiness) is the physical property of a material that returns to its original shape after the stress e.g. external forces (Consider Peak Hours as external forces)
Measured service: Cloud systems automatically control and optimize resource use by leveraging a metering capability. The basic value proposition of cloud computing is to pay as you go, and to pay for what you use. Resource usage can be monitored, controlled, and reported via alerts, dashboards.
Real world example: We pay for electricity as we have used it…
It’s not a Technology…It’s an innovation…Idea….
According to Wikipedia: Cloud computing is the delivery of computing as a service rather than a product, whereby shared resources, software, and information are provided to computers and other devices as a utility (like the electricity grid) over a network (typically the Internet).
