Numa Node configuration for SQL server 2016
When viewed via task manger/ssms it shows 2 Numa nodes. Is my above understanding wrong of 8 Numa nodes?


No, SQL Server 2016 started to ship with automatic numa node partitioning (soft numa) which is what you're seeing here.


  If those are 2 Numa nodes will i have any performance impact compared to current setup?


Impossible to say. Automatic Soft-Numa was added as a default to the product starting with 2016 as certain tasks and threads are on a per-numa basis. Thus, in many environments that had high core count and low numa node count there would be an overall performance improvement by using soft-numa.

Your mileage may and will vary. If you're unsure or don't want to test the new configuration, I would suggest you turn the automatic soft-numa off for now until you can test. This is based on absolutely no data but configuration stabilization between upgrades.

If you want to turn soft-numa off, you can run the following command:

ALTER SERVER CONFIGURATION SET SOFTNUMA OFF