CPU factors are used to differentiate the relative speed of different machines. LSF runs jobs on the best possible machines so that response time is minimized.
To achieve this, it is important that you define correct CPU factors for each machine model in your cluster.
Incorrect CPU factors can reduce performance the following ways.
If the CPU factor for a host is too low, that host may not be selected for job placement when a slower host is available. This means that jobs would not always run on the fastest available host.
If the CPU factor is too high, jobs are run on the fast host even when they would finish sooner on a slower but lightly loaded host. This causes the faster host to be overused while the slower hosts are underused.
Both of these conditions are somewhat self-correcting. If the CPU factor for a host is too high, jobs are sent to that host until the CPU load threshold is reached. LSF then marks that host as busy, and no further jobs will be sent there. If the CPU factor is too low, jobs may be sent to slower hosts. This increases the load on the slower hosts, making LSF more likely to schedule future jobs on the faster host.