Starting in Windows Server 2012 R2 you now have a way to upgrade a cluster to Windows 2016.  The best part is it’s not an OS upgrade, but a rebuild.  The magic is that you can join a Windows 2016 server to a Windows 2012 R2 cluster.  You can upgrade your cluster with as little as one failover and thus very little down time.  Everything stays in compatibility mode until all nodes are upgraded to Windows 2016 and then you upgrade the cluster functional level.  This is great news for those of us running FCIs or AGs.

The Steps

This is just a loose outline of the steps you will need to take.  Don’t worry the video is below!

  • Make sure Node1 is primary
  • Remove Node2 replica from AG
  • Evict Node2 from cluster
  • Install OS on Node2
  • Config NIC Cards
  • Join to Domain
  • Add cluster role
  • Add to cluster
  • Install SQL
  • Enable AlwaysOn
  • Add as replica to AG
  • Failover AG to Node2
  • Make sure Node2 is primary
  • Remove Node1 replica from AG
  • Evict Node1 from cluster
  • Install OS on Node1
  • Config NIC Cards
  • Join to domain
  • Add to cluster
  • Install SQL
  • Enable AlwaysOn
  • Add as replica to AG
  • Failover AG to Node1

Let’s Upgrade a Cluster Together

In this video I upgrade a Windows 2012 R2 cluster with a SQL 2017 AG to a Windows 2016 cluster.

Additional Resources

What’s new in failover clustering: #01 Cluster OS Rolling Upgrade