Web OS 10.0 Application Guide122 n Chapter 6: Server Load Balancing 212777-A, February 2002All of the above issues can be addressed by adding an Alteon Web switch with SLB software. Reliability is increased by providing multiple paths from the clients to the Web switch andby accessing a pool of servers with identical content. If one server fails, the others can takeup the additional load. Performance is improved by balancing the Web request load across multiple servers. Moreservers can be added at any time to increase processing power. For ease of maintenance, servers can be added or removed dynamically, without interrupt-ing shared services.Network Topology RequirementsWhen deploying SLB, there are a few key aspects to consider: In standard SLB, all client requests to a virtual server IP address and all responses from thereal servers must pass through the switch, as shown in Figure 6-4. If there is a path betweenthe client and the real servers that does not pass through the switch, the Web switch can beconfigured to proxy requests in order to guarantee that responses use the correct path (see“Proxy IP Addresses” on page 136).Figure 6-4 SLB Client/Server Traffic Routing Identical content must be available to each server in the same pool. Either of these meth-ods can be used:o Static applications and data are duplicated on each real server in the pool.o Each real server in the pool has access to the same data through use of a shared filesystem or back-end database server.ClientsSwitchInternet NFS ServerServer Pool #1Server Pool #2SwitchAlternate path is not valid withLayer 4 services. IP proxyaddresses must be used on theAlteon Web switchWebSwitchRouterRouter
