We had a 3 node cluster running on HDDs. After migrating to SSDs, we ran a load test but haven't seen any latency difference.
So we are thinking about running a stress test. Is there any threshold or parameters we should set or any general recommendation to find the utmost difference?
Maybe you should run a diagnostics test on the cluster itself instead. There might be some unknown entity(ies) that would be preventing the latency difference. Even on a load test, you should see a significant difference.