Power saving scheduling policy does not really empty as many hypervisors as it could.

Issue

The power saving scheduling policy in RHV 4.2 is implemented in the way that it identifies three groups of hosts. Underutilized, overutilized and normally utilized hosts. The under and over utilized hosts are considered as source hosts for VM live migrations and normally utilized hosts are considered as the destination hosts. This approach has some disadvantages. For example:

• If there are only overutilized and underutilized hosts in the cluster then there will be no migration within the cluster and the overutilized hosts remain overutilized as there are no normally utilized hosts where the VMs could be moved to.
• If the cluster is well balanced then after a while all hosts can fall into the normally utilized hosts and no further hosts will be evacuated to save the power.