Intergraph WebScale User Manual page 8

WebScale™ User's Guide
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NTRODUCTION
WebScale™ Software is an innovative software product that enhances the availability
and scalability of Internet server applications, such as web servers, FTP servers, and
other mission-critical applications. A single Windows NT computer can only provide a
limited level of reliability and scalable performance. However, by combining the
resources of two or more Windows NT computers into a single cluster, WebScale
cluster can deliver the reliability and performance that web servers and other mission
critical applications need. The following diagram depicts a cluster with four host
computers, or servers, within the cluster:
Each host runs a separate copy of the desired server applications, such as web servers,
FTP, telnet, email, etc. For some services, such as web servers, a copy of the
application runs on all hosts within the cluster, and WebScale load-balances the
workload between them. For other services, such as email, only one copy of the service
handles the workload within the cluster. Instead of load balancing these services,
WebScale allows the network traffic to flow to one host, and it moves the traffic to
another host in case of failure.
WebScale clusters together several computers running server applications that use the
TCP/IP networking protocol. WebScale allows all of the machines in the cluster to be
addressed by the same set of cluster IP addresses (while maintaining their existing
addressability using unique, dedicated IP addresses). WebScale distributes incoming
client requests in the form of TCP/IP traffic across the hosts.
To scale server performance WebScale can load-balance the incoming TCP/IP traffic
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