Load balancing

If you deploy an IBM® WebSphere® Application Server cluster within your IBM InfoSphere® Information Server implementation, you can provide a load balancer upstream of the cluster.

InfoSphere Information Server supports many load balancer solutions manufactured by IBM and by other vendors.

The following list highlights the advantages and disadvantages of a load balancer approach.

Advantages of deploying a load balancer
  • Easier deployment because you do not have to set up a network of web servers and then configure the web server plug-ins.
  • More load balancing algorithm alternatives are available. Load balancers often offer more algorithms than the ones provided by web server plug-ins, including advanced load-based balancing strategies that monitor usage levels on individual computers.
Disadvantages of deploying a load balancer
  • Additional configuration is required. You must perform additional configuration to maintain persistent connections between clients and servers (web server plug-ins handle persistent connection maintenance automatically). Also, you must re-configure the load balancer whenever the downstream cluster topology changes (for example, when a node is added or removed).
  • Hardware-based load balancers typically cost more.

To prevent single points of failure at the load balancer level, consider deploying a backup load balancer to take over in case the active one fails.

The following diagram shows an InfoSphere Information Server cluster with a front-end load balancer. A backup load balancer is also deployed.

Figure 1. Cluster with a front-end load balancer
This figure is described in the surrounding text.

You cannot manage the load balancers by using the Deployment Manager.

Make sure to configure session affinity in the load balancer. There are several methods to achieve session affinity. The method you choose depends on the product that you use and the forwarding mechanism that you configure. Mechanisms include media access control (MAC) address forwarding, Network Access Translation/Network Address Port Translation (NAT/NAPT) forwarding, and content-based forwarding. Layer 2 load balancers (load balancers that operate at the MAC layer) generally achieve session affinity by using a "stickiness to source IP address" approach. Layer 3 and higher load balancers (load balancers that operate at the IP layer and above) typically achieve session affinity by using passive cookies or a content-based technique. Session affinity is typically implemented in this manner with HTTP servers. See the load balancer documentation for more information