Cross Cluster Live Migration and Multicluster Scenarios
Cross-cluster live migration is based upon the idea of decentralized live migration which is an advanced variation of a storage live migration, that we covered earlier in this lab. It effectively allows you to migrate a running VirtualMachine between different namespaces within a cluster and between completely remote clusters if so desired.
This can be useful for the following reasons:
Balance Workloads: Distributing virtual machines between clusters helps optimize resource utilization. If one cluster is heavily loaded while another is idle, rebalancing can significantly improve operational efficiency.
Facilitate Maintenance: For environments with multiple clusters, virtual machine migration allows for seamless maintenance. You can move virtual machines off a cluster slated for upgrades or shutdown, ensuring zero downtime for your services.
Expedite Restores: Instant restore capabilities from backup vendors, particularly when coupled with namespace migration, can drastically speed up recovery times. virtual machines can be quickly restored to a temporary location and then migrated to their original namespace and storage.
This lab demonstrates capabilities of Decentralized Live Migration. In this lab, we will walk through the live migration of a VirtualMachine from one Namespace to another. The process of live migrating between namespaces follows the same process as if you were to migrate a VirtualMachine between 2 separate clusters in a multi-cloud environment.
How does it work?
The migration involves two VirtualMachineInstances and two VirtualMachineInstanceMigration objects. Like a storage live migration, disk contents are copied over the network to the receiving VirtualMachine. The key difference is that the receiving virtual machine has a completely separate VirtualMachineInstance. In order to coordinate the migration, the status of the source and target VirtualMachineInstance has to be synchronized. A dedicated synchronization controller, running in the openshift-cnv namespace facilitates communication between the source and target VirtualMachineInstances to complete this sychronization and allow the machine to fully migrate.
Prerequisites
Unlike standard live migration of workloads in an OpenShift Virtualization environment there are some additional prequisites required to enable this functionality.
-
The Migration Toolkit for Virtualization (MTV) Operator must be installed with the feature feature_ocp_live_migration set to true when creating the ForkliftController Custom Resource.
-
You must enable the decentralizedLiveMigration featureGate on the hyperconverged Custom Resource.
Interactive Demo of Cross-Cluster Live Migration
While we were unable to demostrate for you a true cross-cluster live migration due to the limitations of this lab, we would like to invite you to take a few moments to click through this interactive demo. The embedded Arcade demo steps you through a cross-cluster live migration between two remote OpenShift Virtualization clusters managed by a centralized deployment of Red Hat Cluster Management for Kubernetes. The Fleet Management functionality added recently to RHACM 2.16 allows for the easy management of virtual machine workloads across all of your clusters, wherever they are located.
Please enjoy the demonstration:
Congratulations, you have completed this module!