Technical fact 6: How to migrate VMs in the Nutanix cluster after adding a new Lenovo host.

23-aug-2021 10:02:58

Incredible progress has been made by technology in the last couple of years. The future of technology is overwhelming for some, while it can be exciting for others. We have put together some interesting and surprising facts about tech! You might be surprised and amused by what we've discovered. Time to talk about migrating VMs after the addition of a new host in the Nutanix cluster.

Adding a new Lenovo host to an existing Nutanix cluster

For one of our customers, we had to install and add a new Lenovo host to an already existing Nutanix cluster that existed of 4 Lenovo hosts. All these hosts are running Nutanix hypervisor AHV which was already preinstalled on the new host using the foundation software.

After installing the new host's hardware in the rack and correctly connecting everything, we added the host to the cluster. No issues occurred during this process, and the communication between the hosts was perfect. So that went smoothly, thanks to the one-click Prism element interface.

Nutanix Cluster Lenovo Host Migrating VMs
Important: always check the latest version of the CPU firmware!

Now with this Nutanix cluster, each host needed to have two network bridge adapters while there is only one standard configured. For this configuration to be implemented, the Nutanix cluster needs to perform a rolling upgrade, which means all hosts will be rebooted one by one, and the virtual machines will be moved between them. This way our customers won’t experience any downtime on running VM’s/ production.

What problem did we face while migrating the VMs?

The first issue we experienced is that the prechecks to perform this always failed. The cause of this problem was that a couple of the virtual machines were not able not to communicate with the newer CPU version that was installed on the latest added Lenovo host.

Performing VM migrations manually was also an action you couldn’t perform due to this error. Even if you changed the host affinity of all the VM’s to only the older hosts. Host affinity obligates a virtual machine to only move between a few selected hosts. So VM migration wasn’t possible in any way because of the new CPU version.

Bert’s approach for VM migration in the Nutanix cluster.

The only resolution to this issue was power cycling the specific virtual machines which weren’t able to communicate with the last added host with the newer CPU version. Power cycling is a way to restart a vm/hardware when it is in a hung state or when set configuration parameters need to be reinitialized.

Nutanix cluster Lenovo Host Core ICT Migrating VMs
Power cycling virtual machines

The virtual machine then automatically checks for updates when it gets power cycled and installs the new firmware. As a result, the VM can communicate with the newer CPU versions and, therefore, be migrated between the hosts of the Nutanix cluster. This gives us the possibility to configure the two network bridge adapters.

Performing these actions can be difficult because of the downtime of the virtual machines. As best practice, plan a maintenance window which is mostly planned after office hours or during weekends.

After the power cycle, we were able to perform VM migration again which allows us to perform the rolling restarts.

Do you need more information about this topic or maybe you can't solve another IT problem on your own? Please reach out, and we will help you! 

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