The Storm default scheduler assigns component executors as evenly as possible between all the workers (supervisor slots) assigned to a given topology.
Let's consider a sample topology with one spout and one bolt, with both components having two executors. The following diagram shows the assignment of executors if we have submitted the topology by allocating two workers (supervisor slots):
As shown in the preceding diagram, each worker node contains one executor for a spout and one executor for a bolt. The even distribution of executors between workers is only possible if the number of executors in each component is divisible by the number of workers assigned to a topology.
