Cloud application architectures

 The key to cloud computing is the “cloud”—a massive network of servers or even individual PCs interconnected in a grid. These computers run in parallel, combining the resources of each to generate super computing-like power.

the cloud is a collection of computers and servers that are publicly accessible via the Internet. This hardware is typically owned and operated by a third party on a consolidated basis in one or more data center locations. The machines can run any combination of operating systems; it’s the processing power of the machines that matter, not what their desktops look like. 

As shown in above figure, individual users connect to the cloud from their own personal computers or portable devices, over the Internet. To these individual users, the cloud is seen as a single application, device, or document. The hardware in the cloud (and the operating system that manages the hardware connections) is invisible.

This cloud architecture is deceptively simple, although it does require some intelligent management to connect all those computers together and assign task processing to multitudes of users.

As you can see in above figure, it all starts with the front-end interface seen by individual users. This is how users select a task or service (either starting an application or opening a document). The user’s request then gets passed to the system management, which finds the correct resources and then calls the system’s appropriate provisioning services.

These services carve out the necessary resources in the cloud, launch the appropriate web application, and either creates or opens the requested document. After the web application is launched, the system’s monitoring and metering functions track the usage of the cloud so that resources are apportioned
and attributed to the proper user(s).

As you can see, key to the notion of cloud computing is the automation of many management tasks. The system isn’t a cloud if it requires human management to allocate processes to resources. What you have in this instance is merely a twenty-first-century version of old-fashioned data center–based client/server computing. For the system to attain cloud status, manual management must be replaced by automated processes.