The emergence of the virtual host, is a major contribution to Internet technologies, the majority of Internet users in the gospel. Multiple virtual hosts to share the resources of a real host, each user to bear the cost of hardware and network maintenance costs, the cost of communication lines are significantly reduced, the Internet truly become a network that everyone can afford! Now, almost all U.S. companies (including some families) are on the network set up your own web server, in which a considerable part is used in a virtual host. So-called virtual hosting, also called "web space, a computer running the server on the Internet is divided into multiple" virtual "servers, each virtual host has a separate domain name and Internet server (to support the World Wide Web, FTP, e-mail, etc.) functions. Different virtual hosts on a single server is independent, self-management by the user. A server host can only support a certain number of virtual hosts, when more than this number, the user will feel a sharp decline in performance. Virtual mainframe technology used by the Internet server technology to save the cost of server hardware, virtual mainframe technology is mainly used in the HTTP service, one or all of the services of a server logic is divided into a number of service units and external performance for multiple server, in order to take full advantage of server hardware resources. If the classification is a system level, is called the virtual server.