Load imbalance factor

The load imbalance factor (LIF) controls how imbalanced GTM allows the load to be; the factor by which the demand sent to a data center is permitted to exceed the configured value. For example, with a data center traffic allocation of 25 percent and a LIF of 50%, the demand sent to the data center is allowed to grow to 37.5 percent (25% + (25% * 50%) ) before the load balancer starts shifting load away from it.
Note: This option applies only to the following property types:
  • Performance-Based Load Balancing
  • Performance-Based Load Balancing with Load Feedback (targets computed from configured weights)
  • Performance-Based Load Balancing with Load Feedback Based on Liveness Test Download Scores

You can use the LIF with either percent-based load balancing without load feedback, or with one of the load feedback modes that computes targets based on percentages. The LIF is not operational when using XML load objects to report current, target, and maximum loads for a datacenter. In non-load feedback mode, the imbalance factor simply raises the allowed traffic percentage sent to each data center by the requested amount. In loadfeedback mode with automatically computed targets, the LIF raises the targets after they are computed.

Load imbalance is not necessarily bad. The example in "Load Balancing Compared to End User Performance" shows clearly that good end-user performance often requires an imbalanced load. For good performance, you usually need to allow a certain amount of imbalance. The load imbalance factor controls how much imbalance you will permit. Reducing the LIF to below 10% is likely to result in oscillation, meaning the load shifts back and forth between the two data centers.

The default load imbalance factor is 10%.