如下是一篇对Cloud Computing的综述，着重点在硬件的方面。 Cloud Computing， the long-held dream of computing as a utility， has the potential to transform a large part of the IT industry， making software even more attractive as a service and shaping the way IT hardware is designed and Developers with innovative ideas for new Internet services no longer require the large capital outlays in hardware to deploy their service or the human expense to operate They need not be concerned about overprovisioning for a service whose popularity does not meet their predictions， thus wasting costly resources， or underprovisioning for one that becomes wildly popular， thus missing potential customers and Moreover， companies with large batch-oriented tasks can get results as quickly as their programs can scale， since using 1000 servers for one hour costs no more than using one server for 1000 This elasticity of resources， without paying a premium for large scale， is unprecedented in the history of IT Cloud Computing refers to both the applications delivered as services over the Internet and the hardware and systems software in the datacenters that provide those The services themselves have long been referred to as Software as a Service (SaaS) The datacenter hardware and software is what we will call a C When a Cloud is made available in a pay-as-you-go manner to the general public， we call it a Public Cloud; the service being sold is Utility C We use the term Private Cloud to refer to internal datacenters of a business or other organization， not made available to the general Thus， Cloud Computing is the sum of SaaS and Utility Computing， but does not include Private C People can be users or providers of SaaS， or users or providers of Utility C Wefocus on SaaS Providers (Cloud Users) and Cloud Providers， which have received less attention than SaaS U From a hardware point of view， three aspects are new in Cloud C The illusion of infinite computing resources available on demand， thereby eliminating the need for Cloud Computing users to plan far ahead for The elimination of an up-front commitment by Cloud users， thereby allowing companies to start small and increase hardware resources only when there is an increase in their The ability to pay for use of computing resources on a short-term basis as needed (， processors by the hour and storage by the day) and release them as needed， thereby rewarding conservation by letting machines and storage go when they are no longer We argue that the construction and operation of extremely large-scale， commodity-computer datacenters at lowcost locations was the key necessary enabler of Cloud Computing， for they uncovered the factors of 5 to 7 decrease in cost of electricity， network bandwidth， operations， software， and hardware available at these very large economies of These factors， combined with statistical multiplexing to increase utilization compared a private cloud， meantthat cloud computing could offer services below the costs of a medium-sized datacenter and yet still make a good profi
