During the last several years, Web hosting has evolved from simple one-computer system architectures to redundant, load-balanced server farms. A server farm is a network of computer systems. As a Web site demands more and more system resources, the traditional hosting environment is constrained by the limited amount of available resources. There are two basic means of providing more resources: a larger computer system or a distributed computer environment. To provide redundancy and scalability, the distributed computer environment is the preferred method of expanding system resources.

The simplest distributed computer environment consists of two identical Web servers on the same local-area network (LAN) with a load-balancing device (see Figure 3). The load-balancing device is the gateway for all traffic entering and leaving the Web servers. The load balancer directs the incoming traffic to the best performing Web server, to alleviate all resource bottlenecks. With the load balancer as the gateway, the two Web servers appear as one large computing environment to all end-users on the Internet. This simple distributed computer environment can be expanded to accommodate more Web servers, providing greater scalability and consistently high performance levels.

Figure 3. Load Balancing Two Web Servers

The simple distributed-computer environment provides a method for increasing the available computer-system resources, but it will not prevent performance problems associated with specific network issues within the LAN or with the Internet connection at that specific location. To overcome local network problems, Web hosting has continued to evolve into a geographically distributed computing–environment architecture.

By distributing the traffic of a Web site across multiple servers located in dispersed geographic locations, system resources can be added without interruptions in the Web-hosting service, and the Web site can always be available despite LAN or Internet-connection problems. Moreover, with intelligent wide-area network (WAN) load balancing, Web-site performance will increase for all visitors, regardless of their geographic location.

Figure 4 illustrates Web hosting in a geographically distributed computing environment.

Figure 4. Two Site Architectures