OVER VIEW OF CLOUD COMPUTING

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1. Introduction:
The coming shift to cloud computing is a major change in our industry. One of the most important parts of that shift is the advent of cloud platforms. As its name suggests, this kind of platform lets developers write applications that run in the cloud, or use services provided from the cloud, or both. Different names are used for this kind of platform today, including on-demand platform and platform as a service (PaaS). Whatever it’s called, this new way of supporting applications has great potential. To see why, think about how application platforms are used today. When a development team creates an on-premises application (i.e., one that will run within an organization), much of what that application needs already exists. An operating system provides basic support for executing the application, interacting with storage, and more, while other computers in the environment offer services such as remote storage.
If the creators of every on-premises application first had to build all of these basics, we’d have many fewer applications today. Similarly, if every development team that wishes to create a cloud application must first build its own cloud platform, we won’t see many cloud applications. Fortunately, vendors are rising to this challenge, and a number of cloud platform technologies are available today. The goal of this overview is to categorize and briefly describe those technologies as they’re seen by someone who creates enterprises.
Its broadest usage, the term cloud computing refers to the Delivery of scalable IT resources over the Internet, as opposed to hosting and operating those resources locally, such as on a college or university network. Those resources can include applications and services, as well as the infrastructure on which they operate. By deploying IT infrastructure and services over the network, an organization can purchase these resources on an as-needed basis and avoid the capital costs of software and hardware. With cloud computing, IT capacity can be adjusted quickly and easily to accommodate changes in demand. While remotely hosted, managed services have long been a part of the IT landscape, a heightened interest in cloud computing is being fueled by ubiquitous networks, maturing standards, the rise of hardware and software virtualization, and the push to make IT costs variable and transparent.
2. What is cloud computing?

A 'cloud' is an elastic execution environment of resources involving multiple stakeholders and providing a metered service at multiple granularities for a specified level of quality of service). In other words, clouds as we understand them in the context of this document are primarily platforms that allow execution in various forms across multiple resources and potentially across enterprise boundaries.
Cloud computing presents IT organizations with a fundamentally different model of operation, one that takes advantage of the maturity of web applications and networks and the rising interoperability of computing systems to provide IT services. Cloud providers specialize in particular applications and services, and this expertise allows them to efficiently manage upgrades and maintenance, backups, disaster recovery, and failover functions. As a result, consumers of cloud services may see increased reliability, even as costs decline due to economies of scale and other production factors. With cloud computing, organizations can monitor current needs and make on-the-fy adjustments to increase or decrease capacity, accommodating spikes in demand without paying for unused capacity during slower times. Aside from the potential to lower costs, colleges and universities gain the flexibility of being able to respond quickly to requests for new services by purchasing them from the cloud. Cloud computing encourages IT organizations and providers to increase standardization of protocols and processes so that the many pieces of the cloud computing model can interoperate properly and efficiently.
Cloud computing scalability is another key benefit to higher education, particularly for research projects that require vast amounts of storage or processing capacity for a limited time. Some companies have built data centers near sources of renew-able energy, such as wind farms and hydroelectric facilities, and cloud computing affords access to these providers of “green IT.” Finally, cloud computing allows college and university IT providers to make IT costs transparent and thus match consumption of IT services to those who pay for such services.





2.2Cloud Computing is a style of computing which must cater to the following computing needs:
1. Dynamism
2. Abstraction
3. Resource Sharing
2.21. Dynamism:
Your business is growing exponentially. Your computing need & usage is getting bigger with every passing day. Would you add servers & other hardware’s to meet the new demand? Assume, Recession is back & your business is losing customers. The servers & hardware’s you added during last quarter’s peak season is now idle. Will you sale them?
Demand keeps on changing based on world/regional economy, sometimes seasonal traffic burst as well. That’s where Cloud Computing comes to your rescue! You just need to configure & your provider will take care of fluctuating demand.
2.2.2. Abstraction:
Your business should focus on your core competency & should not worry about security, OS, software platform, updates and patches etc. Leave these chores to your provider. From an end users perspective, you don’t need to care for the OS, the plug-ins, web security or the software platform. Everything should be in place without any worry.
2.3.3. Resource Sharing:
Resource Sharing is the beauty of Cloud Computing. This is the concept which helps the cloud providers to attain optimum utilization of resources. Say, a company dealing in gifts may require more server resources during festive season. A company dealing in Payroll management may require more resources during the end or beginning of the month.
The cloud architecture is implemented in such a way that it provides you the flexibility to share application as well as other network resources (hardware etc).

3. Cloud Stacks

Cloud Services can be dived into 3 stacks:

1. Infrastructure as a Service (IaaS)
2. Platform as a Service (PaaS)
3. Software as a Service (SaaS)





3.1 Infrastructure as a Service (IaaS):
IaaS also referred to as Resource Clouds, provide (managed and scalable) resources as services to the user – in other words, they basically provide enhanced virtualization capabilities. Accordingly, different resources may be provided via a service interface: Data & Storage Clouds deal with reliable access to data of potentially dynamic size, weighing resource usage with access requirements and / or quality definition.
Examples: Amazon S3, SQL Azure.
Compute Clouds provide access to computational resources, i.e. CPUs. So far, such low-level resources cannot really be exploited on their own, so that they are typically exposed as part of a “virtualized environment” (not to be mixed with PaaS below), i.e. hypervisors. Compute Cloud Providers therefore typically offer the capability to provide computing resources (i.e. raw access to resources unlike PaaS that offer full software stacks to develop and build applications), typically virtualized, in which to execute cloudified services and applications. IaaS (Infrastructure as a Service) offers additional capabilities over a simple compute service.
Examples: Amazon EC2, Zimory, Elastichosts.