9.18.13.3. Configuring descheduler evictions for virtual machines

Procedure

1. Stop the VM.

2. Configure the KubeDescheduler object with the KubeVirtRelieveAndMigrate profile and enable background evictions for improved VM eviction stability during live migration:

   apiVersion: operator.openshift.io/v1
   kind: KubeDescheduler
   metadata:
     name: cluster
     namespace: openshift-kube-descheduler-operator
   spec:
     deschedulingIntervalSeconds: 60
     profiles:
     - KubeVirtRelieveAndMigrate
     mode: Automatic

3. Optional: To evict pods, set the mode field value to Automatic. By default, the descheduler does not evict pods.

4. Optional: Configure limits for the number of parallel evictions to improve stability in large clusters.

   The descheduler can limit the number of concurrent evictions per node and across the cluster by using the evictionLimits field. Set these limits to match the migration limits configured in the HyperConverged custom resource (CR).

   spec:
     evictionLimits:
       node: 2
       total: 5

   Set values that correspond to the migration limits in the HyperConverged CR:

   spec:
     liveMigrationConfig:
       parallelMigrationsPerCluster: 5
       parallelOutboundMigrationsPerNode: 2

5. Optional: To exclude the VM from eviction, add the descheduler.alpha.kubernetes.io/prefer-no-eviction annotation to the spec.template.metadata.annotations field. The change is applied dynamically and is propagated to the VirtualMachineInstance (VMI) object and the virt-launcher pod.

   Only the presence of the annotation is checked. The value is not evaluated, so "true" and "false" have the same effect.

   apiVersion: kubevirt.io/v1
   kind: VirtualMachine
   spec:
     template:
       metadata:
         annotations:
           descheduler.alpha.kubernetes.io/prefer-no-eviction: "true"

6. Start the VM.