Chapter 1: Foundation

Design and Implementation

• Architecture
• Redundancy
• Another key architectural control is redundancy
• allowing a function to be performed on more than one node, to avoid "putting all the eggs in one basket."
• For example, the design of Figure 7-19 has only one web server; lose it and all connectivity is lost.
• A better design would have two servers, using what is called failover mode.
• In failover mode the servers communicate with each other periodically, each determining if the other is still active. If one fails, the other takes over processing for both of them.