In the DataMiner system requirements document you can find the supported Windows versions for DMAs, but it doesn't mention if there is a problem or if it is not supported that DMAs have different (but supported) Windows versions in a DMS.
Scenario: 1 DMS with 4 DMAs (2 Failover pairs). 2 DMAs (main and backup) have Windows Server 2012 and the other 2 servers (second Failover pair) have Windows server 2016.
Is this scenario supported or should all DMAs within a DMS have the same OS version?
While it's best practice to have your clustered DataMiner Agents running the same OS version, there are no technical implications if they are running different OS versions (as long as it's a supported version).
Do note that even though the OS version might be different of the DataMiner Agents inside the cluster, the DataMiner software version needs to be the same in the entire DMS.