You can perform the cluster upgrade directly from 2012 R2 to 2019 without needing to upgrade to 2016 first.
- Install Windows Server 2019 on the third node.
- Configure Hyper-V, Failover Cluster, Storage, and Network on the third node.
- Add the third node to the current cluster.
- Migrate all VMs from Node 1 to Node 3 using Live Migration.
- Drain and evict Node 1 from the cluster.
- Reformat the Node 1 C drive and install Windows Server 2019.
- Configure Hyper-V, Failover Cluster, Storage, and Network, and add Node 1 back to the cluster.
- Live Migrate the VMs from Node 2 to Node 1.
- Drain and evict Node 2 from the cluster.
- Reformat the Node 2 C drive and install Windows Server 2019.
- Configure Hyper-V, Failover Cluster, Storage, and Network, and add Node 2 back to the cluster.
- Distribute the VMs across the three nodes as needed.
- After all, nodes are running Windows Server 2019, update the cluster functional level to the latest version using the following PowerShell command:
Update-ClusterFunctionalLevel
By following this plan, you can minimize downtime and ensure that your production VMs remain operational during the upgrade process. Remember to have a backup of your VMs and cluster configuration before starting the upgrade process, just in case you need to restore the environment.