Virtual server appears as server with complete server functionalities. But it is not a real server without the dedicated server hardware system.

There are two architecture approaches for the virtual server. One builds itself on a cluster of real servers. The topology of cluster is transparent to end users, and the users interact with the system as if it were only a single virtual server. The real servers may be interconnected by high-speed LAN or by geographically dispersed WAN. The front-end of the real servers is a load balancer, which schedules requests to the different servers and make parallel services of the cluster to appear as a virtual service on a single IP address. Linux/UNIX virtual server is based on this architecture. This type of Virtual Server can be used to build highly scalable and high available network services, such as a scalable web, mail or media service.

The other approach is the virtual machine approach which enables users to run multiple operating systems concurrently on a single physical server, providing for much more effective utilization of the underlying hardware. Microsoft® Virtual server 2005 is based on such technology.

The following are key features of a virtual server:

• Appears to have its own processes, users, files and provides full root accessï¼›
• Each has its own IP addresses, port numbers, tables, filtering and routing rulesï¼›
• Each could have its own configuration files for the system and app softwareï¼›
• Each could have its own versions of system libraries or modify existing onesï¼›

Each could delete, add, modify any file, including files in /root, and install its own application software or custom configure/modify root application software.

Virtual Switching

Related Terms: Virtual Machine, Microsoft Virtual Server 2005