My main production server has four NUMA nodes with two SQL Server 2012 instances on it. One of the instances has the CPU affinity set to use only one NUMA node, and sys.dm_os_nodes reflects that correctly. The other instance has no affinity settings, so it should show all 4 NUMA nodes as online, I would think, but it shows Node 3 as offline, which happens to be the node that's online for the other instance. Is there a bug in SQL Server 11.0.3128 (Enterprise)?