5.5. Load Balancing Policy: Power_Saving

A power saving load balancing policy selects the host for a new virtual machine according to lowest CPU and memory utilization. The maximum service level is the maximum CPU and memory utilization that is allowed for hosts in a cluster, beyond which environment performance will degrade. The minimum service level is the minimum CPU and memory utilization allowed before the continued operation of a host is considered an inefficient use of electricity. The Power_Saving policy allows an administrator to set a maximum and minimum service level for running virtual machines. The length of time a host is allowed to continue at this maximum or minimum service level before the Red Hat Enterprise Virtualization Manager intervenes is also set by an administrator. If a host has reached the maximum service level and stays there for more than the set time, the virtual machines on that host are migrated one by one to the host that has the lowest CPU and memory utilization. The process continues until the host CPU and memory utilization is below maximum service level. If a host CPU or memory utilization falls below the minimum service level the virtual machines are migrated to other hosts in the cluster if their maximum service level permits. When an under-utilized host is cleared of its remaining virtual machines, the Manager will automatically power down the host machine, and restart it again when load balancing requires or there are not enough free hosts in the cluster.