The cloud is just a metaphor for the Internet.
In a very simple words ‘Cloud computing’ lets you keep information on a remote server (the cloud), instead of trapped in a computer hard drive. You can access your data from a smartphone, a tablet, a laptop, or a desktop—wherever you have an Internet connection.
Cloud computing is the next stage in the Internet’s evolution, providing the means through which everything — from computing power to computing infrastructure, applications, business processes to personal collaboration — can be delivered to you as a service wherever and whenever you need.
The “cloud” in cloud computing can be defined as the set of hardware, networks, storage, services, and interfaces that combine to deliver aspects of computing as a service.
Benefits of Cloud:
1. Flexibility – The services can be scaled up and down very easily.
2. ‘Pay-as you-Use’ model of billing where you pay only for the services you use.
3. API’s for the development of customized application for private or public use, which provides and extension to the already available services.
4. Let’s you focus more on your business and core activity:You are tension-free from procurement, deployment and maintenance of the infrastructure by yourself on your premises.
Different Service Models offered by Cloud
1. IaaS (Infrastructure-as-a-Service) – means you’re buying access to raw computing hardware over the Net, such as servers or storage. Since you buy what you need and pay-as-you-go, this is often referred to as utility computing. Ordinary web hosting is a simple example of IaaS: you pay a monthly subscription or a per-megabyte/gigabyte fee to have a hosting company serve up files for your website from their servers.
2. Saas (Software-as-a-Service) – means you use a complete application running on someone else’s system. Web-based email and Google Docs are perhaps the best-known examples. Zoho is another well-known SaaS provider offering a variety of office applications online.
3. PaaS (Platform-as-a-Service) – means you develop applications using Web-based tools so they run on systems software and hardware provided by another company. So, for example, you might develop your own e-commerce website but have the whole thing, including the shopping cart, checkout, and payment mechanism running on a merchant’s server. Force.com (from salesforce.com) and the Google App Engine are examples of PaaS.
Various models of deployment
1. Private Cloud – Private cloud is cloud infrastructure operated solely for a single organization, whether managed internally or by a third-party and hosted internally or externally.
2. Public Cloud – A cloud is called a “public cloud” when the services are rendered over a network that is open for public use.
3. Community Cloud – shares infrastructure between several organizations from a specific community with common concerns (security, compliance, jurisdiction, etc.), whether managed internally or by a third-party and hosted internally or externally.
4. Hybrid Cloud – Hybrid cloud is a composition of two or more clouds (private, community or public) that remain unique entities but are bound together, offering the benefits of multiple deployment models.