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Top1. Introduction
The invention of cloud computing is one of the major advances in the history of computing. It is the latest technology and companies are using the cloud computing in their administrative reforms to make them effective and efficient. It enables business to deliver new services, enter into new markets, get closer to customers and make employees more productive. Cloud computing has an infinite amount of resources such as CPU, memory and disk etc. It enables and facilitates the provisioning of various types of services and allows the users and providers to access the specified resources according to their needs. These resources are offered to the users at a competitive rate and customers pay for their actual usage without upfront costs. Due to its advantages, cloud has been increasingly adopted in many areas such as banking, e-commerce, retail industry and academic purpose. Cloud proves to be very useful for the startup companies as it gives them an opportunity to host their applications in the cloud. Thus, eliminating the overhead of procuring traditional infrastructure resources which typically take several months. It is a computing solution based on Internet where shared resources are provided like electricity distributed on the electrical grid. Machines in the cloud are configured to work together. Various applications use the collective computing power of the machines as if they are running on a single system. Allocation of resources on demand is a function of cloud computing which facilitates the use of the system's cumulative resources and hence eliminates the need to assign specific hardware to a task. Before the advent of cloud computing, websites and server-based applications were executed on a specific system. With cloud computing, resources are used as an aggregated virtual computer. This blended configuration provides an environment where applications execute independently without regard for any particular configuration. Cloud computing is the latest technology in which a lot of research work is going on.
Clouds are complex, large-scale and heterogeneous distributed systems (e.g., consisting of multiple data centers, each containing thousands of servers and peta bytes of storage capacity) which needs to be automated and integrated with intelligent strategies for dynamic provisioning of resources in an autonomic manner. Cloud computing providers offer their services according to several fundamental models. In industry, these services are referred as Infrastructure as a Service (IaaS) in which a computing resource such as processing power or storage is provided, Platform as a Service (PaaS) in which tools for the development of adapted applications are provided and Software as a Service (SaaS) in which the service provides functionality similar to an end-user application. These services delivers computing infrastructure including physical machines, networks, storage and system software as virtualized computing resources over Internet. Cloud management is responsible for management of all resources used by all the applications deployed in the cloud. Main cloud computing service providers are Amazon Elastic Compute Cloud (Amazon EC2), Google App engine and Salesforce respectively. In a cloud computing environment, the organization running an application does not typically own the physical hardware used for the applications. In fact, while running applications in the cloud, an organization does not usually know exactly where the computation work of the applications is being processed. Cloud computing provides an organization with considerably more flexibility and scalability to satisfy computing needs.
In early days, email services were provided to the company’s personnel. The company used to have a server hardware sitting somewhere in the company (i.e. a server with CPU, RAM, HDD). On that hardware, a server operating system (e.g. Windows NT Server 4, in those days) was installed. Then on top of Windows NT Server 4, Microsoft Exchange Server (Email server) was installed. That was all like a bundle. So if anything goes wrong with the operating system or the underlying hardware, the exchange server will halt and the company’s personnel will no longer be able to use the email services. The idea of cloud computing is that we are trying to distinguish the application, the services and the hardware from themselves and this is where the power of virtualization comes. Virtual computing puts the operating system in its own container that is running on hardware. Its benefit is, if something gets failed on a particular hardware, the instance of operating system automatically migrates to another piece of hardware on another server’s system.