Virtual Machine and Host High Availability - Getting Started with Red Hat Enterprise Virtualization - page 115

The cluster policy
The cluster policy will allow you to distribute the load of virtual machine across hosts in
the cluster. By default, Cluster Policy is set to None .
Perform the following steps to define a new cluster policy:
1. Log in to the Administrator console, and navigate to the Clusters tab.
2. Select the appropriate cluster from the list for which you want to define the cluster
policy, right-click on it, and select Edit .
3. In the new Edit Cluster window, move to Cluster Policy , and select any of the
following options relevant to your environment:
◦ Evenly_Distributed : Distribute the CPU load evenly across the hosts in
the cluster. If any of the hosts in the cluster breach the defined maximum
service level, the additional virtual machine will not start on the specific
host.
◦ CpuOverCommitDurationMinutes : This option allows you to define the
time interval before the cluster policy takes an action. This is mainly to
protect the unnecessary virtual machine migration due to a temporary
spike in the CPU load.
◦ HighUtilization : This is defined in percentage. If the host CPU reaches
this defined limit or crosses it, then the RHEV Manager will start to mi-
grate the virtual machine to another underutilized host until the defined
CPU limit of the host falls under an accepted threshold.
◦ Power saving : Setting the policy will distribute the CPU load across sub-
sets of other hosts. In short, if any hosts in the cluster fall under the low
CPU utilization limit for the defined time interval, then the RHEV Man-
ager will start to migrate the running virtual machine to another underutil-
ized host and allow us to safely power down the hosts that are not running
any virtual machines. This is extremely useful during non-business hours
where systems are running with less load in order to save power. Note that
if the other active host CPU limit reaches the high utilization CPU limit,
then the additional virtual machine will not start on the host.