【正文】 world via the Internet.So, despite superficial similarities, networking puting and outsourcing are not cloud puting.What Cloud Computing IsKey to the definition of cloud puting is the “cloud” itself. For our purposes, the cloud is a large group of interconnected puters. These puters can be personal puters or network servers。 Spreadsheets, Google Calendar, Gmail, Picasa, and the like. All of these applications are hosted on Google’s servers, are accessible to any user with an Internet connection, and can be used for group collaboration from anywhere in the world.In short, cloud puting enables a shift from the puter to the user, from applications to tasks, and from isolated data to data that can be accessed from anywhere and shared with anyone. The user no longer has to take on the task of data management。 with client/server puting, all the control rested with the mainframe—and with the guardians of that single puter. It was not a userenabling environment.PeertoPeer Computing: Sharing ResourcesAs you can imagine, accessing a client/server system was kind of a “hurry up and wait” experience. The server part of the system also created a huge bottleneck. All munications between puters had to go through the server first, however inefficient that might be.The obvious need to connect one puter to another without first hitting the server led to the development of peertopeer (P2P) puting. P2P puting defines a network architecture in which each puter has equivalent capabilities and responsibilities. This is in contrast to the traditional client/server network architecture, in which one or more puters are dedicated to serving the others. (This relationship is sometimes characterized as a master/slave relationship, with the central server as the master and the client puter as the slave.)P2P was an equalizing concept. In the P2P environment, every puter is a client and a server。 because any puter can function in that capacity when called on to do so.P2P was also a decentralizing concept. Control is decentralized, with all puters functioning as equals. Content is also dispersed among the various peer puters. No centralized server is assigned to host the available resources and services.Perhaps the most notable implementation of P2P puting is the Internet. Many of today’s users forget (or never knew) that the Internet was initially conceived, under its original ARPAnet guise, as a peertopeer system that would share puting resources across the United States. The various ARPAnet sites—and there weren’t many of them—were connected together not as clients and servers, but as equals.The P2P nature of the early Internet was best exemplified by the Usenet network. Usenet, which was created back in 1979, was a network of puters (accessed via the Internet), each of which hosted the entire contents of the network. Messages were propagated between the peer puters。 it’s the processing power of the machines that matter, not what their desktops look like.As shown in Figure , individual users connect to the cloud from their own personal puters 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 puters together and assign task processing to multitudes of users. As you can see in Figure , it all starts with the frontend 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 puting 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 twentyfirstcentury version of oldfashioned data center–based client/server puting. For the system to attain cloud status, manual management must be replaced by automated processes.