寫了一堆，雖然精闢，但在都放在introduction裏面也不合適，刪吧。
放在這兒紀念一下。
For past years, numerous leading companies and academic groups have successfully established their own free and commercial cloud services, and encourage people and organizations to do everything online, such as data storage, processing and management[[i]]. People also become accustomed to using the computing resources of clouds just on “thin” devices, such as on netbooks, tablet computers (e.g. iPad) and cell phones.
Unlike traditional network computing, the client’s computer resources in cloud have been further concentrated in cloud platform [[ii]], and the Clients just remain minimal computing resources, especially storage resources. The storage capacities of iPhone4 and iPad just are 16-64GB, whereas a standard PC is 500GB-2TB.
Thus this novel networking computing architecture imposes higher requirements on the manageability of computing resources in cloud platforms.
On the other hand, virtual machine(VM) techniques have been widely used to virtualize, redistribute and manage the computing resources of the clouds, especially in private clouds, as a capital infrastructure of cloud computing. In the meantime, unlike the commercial products from VMware and Microsoft, open source VM techniques, such as Xen, have received extensive attention in many academic and commercial clouds.