Introduction to using external hardware devices for load balancing

You can load balance FMS data using external hardware load balancers. These devices exist within the network topology, but are not part of the FMS system. This load balancing method allows you to route requests from multiple clients among a number of FSCs. You must configure the devices so that each target server receives an equal load. Your goal is to minimize overall response time at the requesting clients by routing requests to the most available server. Configure FMS to recognize these third-party hardware devices using the loadbalancer XML element in the fmsmaster_fscid.xml file. Identify which FSCs are within the scope of a load balancer using the loadbalancerid attribute of the fsc element. Each loadbalancer XML element that contains one or more resources (volume, logvolume, transientvolume, or accesson) or one or more filestore entries must have at least one FSC in its scope. FSCs within the scope of the specified load balancer serve all resources declared in the loadbalancer element, and perform the routing behaviors (entryfsc, exitfsc, assignedfsc) attributed to the load balancer. This prevents FSCs within the scope of a load balancer from forwarding requests back to the load balancer. To clients and FSCs not within the scope of the specified load balancer, the load balancer appears as a single FSC which serves all of the balanced resources and exhibits the load balancer’s routing behaviors. Direct FSC routing, intergroup routing, and intragroup routing all function on this basis. Thus clients request the balanced resources only from the load balancer. Note The loadbalancer XML element is similar to the fsc XML element. The significant difference is that this element cannot be used as the ID of the FSC element in a local FSC configuration file. This is because the loadbalancer XML element must always represent external hardware, never an actual FSC. This element can only be used in the primary configuration file (fmsmaster_fscid.xml). You can use the loadbalancer ID as a value for any of the following attributes within the FSC group in which it is declared: entryfsc fscid exitfsc fscid assignedfsc fscid fsc loadbalancerid The loadbalancer element can contain any of the following child elements: connection fccdefaults fscdefaults filestore Any type of resource, such as volume, logvolume, transientvolume, accesson Load balancers support health checking for their servers. Health checking is generally configured to use a particular URL within the back-end servers. Because FSC servers support few requests that do not require tickets, many default health checks return HTTP 400 errors that load balancers may interpret to mean service is unavailable. To avoid these errors, Siemens Digital Industries Software recommends using HTTP HEAD or GET requests for /Ping or /favicon.ico resources. These requests return an HTTP 200 status and verify the FSC is alive. For WebSEAL, this configuration is controlled using the ping-uri configuration element, documented in the WebSEAL product documentation.