Module 3: VM Live Migration

In this module, we will explore how application workload running on OpenShift can be migrated "live" between worker nodes.

Live migration is the process of moving a running virtual machine (VM) to another node in the cluster without interrupting the virtual workload. Live migration enables smooth transitions during cluster upgrades or any time a node needs to be drained for maintenance or configuration changes.

By default, live migration traffic is encrypted using Transport Layer Security (TLS).

Reasons for VM migration:

Load Balancing: VMs can be moved to host machines with lower usage if their host becomes overloaded or if another host is under-utilized. Through load-balancing, you can improve VMs capacity and network performance.

Energy savings: VMs can be redistributed to other hosts, and the unloaded host systems can be powered off to save energy and cut costs.

Geographic migration: VM can be moved to another physical location for lower latency or when required for fault tolerance or disaster recovery.

Live migration requirements

The cluster must have shared storage with ReadWriteMany (RWX) access mode.
The cluster must have sufficient RAM and network bandwidth.
If a VM uses a host model CPU, the nodes must support the CPU.
Configuring a dedicated Multus network for live migration is highly recommended. A dedicated network minimizes the effects of network saturation on tenant workloads during migration

Learning objectives

By the end of this module, you will be able to:

Migrate virtual machine between worker nodes
Migrate a virtual machine to a new storage class

Exercise 1: VM live migration

In this exercise, you will create a new virtual machine and migrate it between worker nodes in an OpenShift cluster.

Verify

Confirm that you have a virtual machine running with a storage class that is RWX. If not, you will need to create a new virtual machine and customize the VM’s boot volume to a storage class that is RWX enabled. ceph RBD is capable of RWX.

Create or Select a Virtual Machine

Create a new Virtual Machine (VM) or select a VM from a previous you created in a previous section of this lab.

Once you have a VM, make sure the VM is in the running state.

Figure 1. List Virtual Machines

Figure 2. Running Virtual Machines

Also, take note of the "node" the Virtual Machine is running on.

Figure 3. Virtual Machine Node

Now select actions, migration, Compute:

Figure 4. Virtual Machine Migration

At this point you will see a dialog box: Migrate VirtualMachine to a different Node. Select Specific Node and then choose a new node for the target migration. Then click Migrate Virtual Machine

Figure 5. Virtual Machine Migration Node

The status of the VM will change from running to migrating but can be quick so it might flash very briefly from running to migrating and back to running

Once it is complete, check the node the VM is running on. It should be the node you selected.

Exercise 2: VM live storage migration

In this exercise, you will perform a storage migration from the existing storage class to a new storage class.

As with "exercise-1", select a virtual machine you created and check its storage class. In this exercise, we will migrate to a new storage class.

Navigate to Storage, StorageClasses:

Figure 6. Virtual Machine Storage Classes

ocs-storagecluster-cephfs and ocs-storagecluster-ceph-rbd-virtualization are both good classes for virtual machines.

Navigate back to your list of virtual machines and select a running VM.

You can check the storage class in use by selecting Configuration, Storage

Figure 7. Virtual Machine Storage Class

Now navigate back to the Overview and select migration, storage

Figure 8. Virtual Machine Storage Migration

This will start the dialog box:

Figure 9. Virtual Machine Storage Migration Dialog

Select The entire VirtualMachine and next

Figure 10. Virtual Machine Storage Migration New Class

Next and then Migrate VirtualMachine:

Figure 11. Virtual Machine Storage Migrate

Now the migration will show running

Figure 12. Virtual Machine Storage Migration Running

when completed

Figure 13. Virtual Machine Storage Migration Done

Verify

Navigate back to configuration, storage and verify the storage change:

Figure 14. Virtual Machine Storage Migration Varify

Learning outcomes

By completing this module, you should now understand:

How to navigate the OpenShift Virtualization interface and Start Virtual Machine Migrations
How to start a virtual machine compute migration
How to start a virtual machine storage migration

Module summary

You have successfully explored the OpenShift Virtualization environment for migrations.

What you accomplished:

Navigated the OpenShift Virtualization dashboard for migrations
Examined IBM Fusion storage classes and running nodes.
Migrated a virtual machine to a new worker node.
Changed a virtual machines storage class.

Next steps:

Module 4 will cover IBM Fusion Backup and Restore service