Live Migration Support for VMs¶

Live migration is a process during which a running VMI moves to another compute node while the guest workload continues to run and remain accessible.

Enable the Live Migration Support¶

Live migration is enabled by default in recent versions of KubeVirt. Versions prior to v0.56 must be enabled in the feature gates. The feature gates field in the KubeVirt Custom Resource must be expanded by adding the live migration to it.

Limitation for live migrations:

VMs using a PVC must have a shared RWX access mode to be live migrated.
Live migration is not allowed with a pod network binding of bridge interface type ().
Live migration requires ports 49152, 49153 to be available in the virt-launcher pod. If these ports are explicitly specified in a masquarade interface, live migration will not function.

Initiate Live Migration¶

Live migration is initiated by posting a VMIM object to the cluster. The example below starts a migration process for a virtual machine instance vmi-fedora.

cat <<EOF> migration.yaml
apiVersion: kubevirt.io/v1
kind: VirtualMachineInstanceMigration
metadata:
  name: migration-job
spec:
  vmiName: vmi-fedora
EOF

kubectl apply -f migration.yaml

Use virtctl to initiate Live Migration¶

Live migration can also be initiated using virtctl.

virtctl migrate vmi-fedora

Live Migration for SRIOV based VMs¶

It is possible to live migrate SR-IOV based VMs, but there are some limitations:

Specify the MAC address statically and on host the name of the SR-IOV interface should be same on source and target host.
Specify the Static IP address.

Below is an example manifest for SR-IOV VM using a static MAC address:

apiVersion: kubevirt.io/v1
kind: VirtualMachine
metadata:
  labels:
    special: vmi-sriov-network
  name: vmi-sriov-test-vm
spec:
  running: true
  template:
    metadata:
      labels:
        kubevirt.io/size: small
        kubevirt.io/domain: fedora
    spec:
      domain:
        cpu:
          cores: 4
        devices:
          disks:
          - name: containerdisk
            disk:
              bus: virtio
          - name: cloudinitdisk
            disk:
              bus: virtio
          interfaces:
          - macAddress: "02:00:00:00:00:01"
            name: sriov-net1
            sriov: {}
          rng: {}
        resources:
          requests:
            memory: 1024M
      networks:
      - multus:
          networkName: sriov-net1
        name: sriov-net1
      volumes:
      - containerDisk:
          image: docker.io/kubevirt/fedora-cloud-container-disk-demo:devel
        name: containerdisk
      - cloudInitNoCloud:
          networkData: |
            ethernets:
              sriov-net1:
                addresses:
                - 10.10.10.12/24
                gateway: 10.10.10.1
                match:
                  macAddress: "02:00:00:00:00:01"
                nameservers:
                  addresses:
                  - 10.96.0.10
                  search:
                  - default.svc.cluster.local
                  - svc.cluster.local
                  - cluster.local
                set-name: sriov-link-enabled
            version: 2
          userData: |-
            #!/bin/bash
            echo "fedora" |passwd fedora --stdin
        name: cloudinitdisk

Below is an example manifest to initiate the live migration:

apiVersion: kubevirt.io/v1
kind: VirtualMachineInstanceMigration
metadata:
  name: migration-job-1
spec:
  vmiName: vmi-sriov-test-vm