We are currently using Active Directory 2008R2 and will be upgrading to AD 2016. I'm trying to determine if there is any known compatibility issues when running older versions of SQL Server (2000 and 2005) when upgrading to AD 2016. Has anyone been through this process? Most of our db servers are using SQL 2008 > 2016, but a few still runs with 2000/2005. Thanks
I have not gone through this process directly, but have worked with querying AD in a modern environment and a less modern environment. I believe that the OLE DB Provider remains compatible between the older and newer versions of AD. Also I would not expect the loss of any commonly used (at least in my experience) properties, which would be the other risk.
If you do run into trouble, however, I would be prepared to migrate the databases to a newer instance of SQL Server running those DBs at a lower db compatibility level. This will still be challenging, as I think you can only go back to 100 (2008). However, from a mitigation standpoint I would suggest trying to go this route regardless. This would also allow you to retire the older instances (and likely old servers they are running on). Why not make a bigger project even bigger (though you can do it ahead of time, so it doesn't all fail at once).
I will qualify this with my of querying AD had been generally focused on getting basic user properties and group membership, and do it so infrequently I have to go look everything back up. And it's been a few years since I have to do much Windows Admin work.