Cloud computing is the latest effort in delivering service based computing resources. It provides a distributed computing platform over the network to share computing resources rather than having local or personal devices for handling applications. The concept of cloud shares different characteristics from peer to peer, distributed computing, grid computing, client server model, mainframe and utility computing. Generally, cloud can be classified to private cloud, used by a single organisation and a public cloud, kept open over the network for public use. It provides low cost computing by sharing remotely located computing devices. Here the machine or the actual hardware is located in different location. And the user, having permission can connect to the machine through a communication network, like LAN, WAN or internet. The user uses remote computing resources to do any computing task, store data or run applications. Here multiple instances of a single application can run simultaneously on connected computing devices.
Cloud follows three fundamental service models to provide various services to the user as a virtual machine. The most basic service provided by the cloud is “Infrastructure as a Service” (IaaS). In this model it provides the access of the physical machine and other computing devices from different location. In an enterprise IaaS can be used as a very cost effective and the scalable IT solution where the expenses, complexity and overhead to manage the underlying hardware can be outsourced to the cloud provider. The “platform as a Service” (PaaS) is the other service model, which is actually built on the concept of IaaS. PaaS provides access to a platform or operating system installed in a virtual machine to the user for computing. Last of all, “Software as a Service” (SaaS), is a business model, where the user can get the installed applications and databases on the abstract of PaaS. Cloud can also provide “Network as a Service” (NaaS), “Communication as a Service” (CaaS), “Identity as a Service” (IaaS) or even “Anything as a Service” (XaaS).
Privacy and security of information is the biggest concern in cloud, as the enterprise have to keep data in different location in order to use the service from a cloud provider. The dependencies on the service provider is one more disadvantage of cloud computing. Sometime migration from one provider to another become impossible as they use different service policies. The users of the organisation, who are using cloud have limited control over the software, platform and hardware as the system runs on a remote virtual environment. But on the other hand, cloud globalizes the workspace by allowing the user to access anything from anywhere. It provides ease of integration, as introduction to the new user is instantaneous. It scales up or down the resource as per requirements and saves energy. Moreover, Cloud minimizes the complexity of licensing the software and operating system. It minimizes cost of resources by making them shared over the network. So, it is not a technology to only make money, but also keep it with.