What is the best approach to migrate a large database running on Windows 2008R2 and SQL Server 2012 to new hardware running Windows Server 2012R2 and SQL Server 2014?

I was hoping that I could add the new servers to the Windows Server Fail-over Cluster (WSFC), even though they are not the same OS version. If that is possible, then add the Availability Group from the old cluster to the new cluster and add a Availability Replicas for the database and start failing over to the new hardware. Once there remove the old servers from the AG and then from the WSFC.

AlwaysOn 2014 is working on the new machines.

The new servers were configured in their own WSFC, and added to the old Availability Group.  This resulted in the database synchronizing to the new server, but never able to come online. I am assuming the reason is that there is no heartbeat between the old and new servers as they are in different WSFC's.  

Any best practice advice or guidance is appreciated.

Hi  SQLMonger,

Based on your description, you want to migrate  SQL Server 2012 AlwaysOn Availability Group in Windows Server 2008 R2 Failover Clustering (WSFC) cluster to SQL Server 2014 AlwaysOn Availability Group in Windows Server 2012 R2 Failover Clustering (WSFC) cluster, right?

If that is the case, you can follow the steps in Cross-cluster Migration of AlwaysOn Availability Groups for Operating System Upgrades word document to migrate SQL Server AlwaysOn Availability Groups to another Windows Failover Cluster.

However, if you mean to migrate a large database from a SQL Server 2012 instance to a SQL Server 2014 instance, you can consider to use other methods such as backup/restore, log shipping and so on. For more details, please review this similar blog: Options to Move a Big SQL Server Database to a New Drive with Minimal Downtime. Also execute the script in this KB article to transfer the logins between instances of SQL Server on different servers.

Thanks,
Lydia Zhang

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