What is virtual server?
Virtual server is a highly scalable and highly available server built on a cluster of real servers. The architecture of server cluster is fully transparent to end users, and the users interact with the system as if it were only a single high-performance virtual server. Please consider the following figure.
The real servers may be interconnected by high-speed LAN or by geographically dispersed WAN. The front-end box before the real servers is a load balancer, which schedules requests to the different servers and makes parallel services of the cluster to appear as a virtual service on a single IP address. Scalability is achieved by transparently adding or removing a node in the cluster. High availability is provided by detecting node or daemon failures and reconfiguring the system appropriately.
Goals
The basic goal of the Linux Virtual Server Project is to:
Build a high-performance and highly available server for Linux using clustering technology, which provides good scalability, reliability and serviceability.