Testing DNS Performance

I've installed packetbeat on a windows dns server to try and get some insight into requests and performance

Is there anything specific I should be looking at from the dashboard to find out if there are issues

I'm looking at the response codes and the SERVFAIL numbers seem to be quite high, this is a few days worth
NOERROR 3,810,728
SERVFAIL 572,398

I'm not sure how to interpret the [Packetbeat] DNS Tunneling ECS dashboard, the highest number is showing local domain

As always thanks for your help