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　　Bring the "virtual" into reality - virtualization technology analysis

　　In server circles, virtualization brings higher utility to users at the component and system level. This leads to a server environment of high reliability, a transparent workload balance, dynamic migration, error auto-isolation with system auto-reconstruction, and a more concise, centralized server resource distribution management mode.

　　As increasing demand from the enterprise to solve such problems as detailed cost control of IT system, larger amount servers, low server utility and bringing x 86 server reliability to the 5th digit, virtualization technology can offer a solution. It promises to reduce the number of servers required, promote server resource benefits to a large scale, and the improved server reliability drives a strong need for server platforms based on x86 architecture. Especially as the x86-server becomes increasingly more crucial to industries and applications, this demand appears contines to become more urgent.

　　In fact, it has been several decades since virtualization first turned up. In 1959, Christopher Strachey published an academic paper named Time Sharing in Large Fast Computers, in which he initially mentioned the basic concept of virtualization. Although the author thought that the report was "mainly on multi-program technology (avoid external restrictions)". Between 1960 and 1979, IBM and some other companies developed virtualization tech, but same as Strachey, they focused on performance. If you are interested in this, please review the article The History of Virtualization on our website.

　　The following 10 years saw great improvement on micro-processor technology. IT gradually evolved to a "general" compute mode. At that time, most mainframes and mini infrastructures were replaced by the PC server in light of high efficiency and low cost, and in an ad hoc manner for new application deployment. Due to the ever increasing speeds and performance of microcomputers, initial deployment costs of new servers were affordable. IT managers began to use the improved performance to meet application needs by simply adding more servers. In fact, as long as certain department wanted to deploy a new application, it would also ask for a new server. And this application would typically be approved by IT managers. As a result, people rarely tried to use virtualization in x86 server environments. Essentially, because every group had their own server, they felt that it was unnecessary to change this process.

　　This directly led to a sharply increasing number of servers. From 1990 till now, this situation has been getting worse. On one hand, many servers in data centers are in full use, giving the average utilization of roughly 15%. On the other hand, maintenance cost of large data centers soared which took a lot of money to maintain electricity, space and cooling needs, and most expensive of all are the operation and management resources required to maintain the infrastructures.

　　Low efficiency and the ever-increasing costs impede enterprises' ability to change to "a compute mode in direction of applicability", which aims at constructing infrastructure in terms of a whole solution. While plan and deployment methods in the perspective of peak workload will be out of date. Many HW and SW manufacturers integrated corresponding technologies and functions in their products, including function, power, and virtualization management.

　　Virtualization Status Quo

　　In the late 1990s, VMware and other virtualization SW manufacturers initially built a virtualization road for x86 servers. They developed a virtualization monitor SW solution (VMM, alias Hypervisor) which achieved PC server platform virtualization. VMM/Hypervisor is a middle software level running between basic physical server and OS. It allows multi operations and applications to share hardware. However, in this kind of pure SW "full virtualization "mode, the VMM controls various key platform resources, then allocates to every client OS in order to avoid conflicts. It requires binary translation (a kind of complex operation on changing client OS binary), for the purpose of handling virtualization-relevant operation. A popular technology to improve virtualization performance, called "Paravirtualization" can modify client OS source code to allow interfaces for virtualization to be more efficient. But the problem is this modification is fairly complicated, calling for much time and human resource input from SW vendor, integrator, and IT manager to carry out system optimization. Furthermore, VMM cannot run unmodified or proprietary client OS.

　　VMM/Hypervisor is a middle software level running between basic physical server and virtual machine (VM) OS. VMM provides every VM OS with the hardware interface which makes the VM OS think that it controls the physical server. This allows multiple VM OS's to share the server hardware. The VMM simulates every physical server functions relative to the VM OS and the applications that run on that VM OS.