As Exchange 2019 is now supported on Windows 2019 core, so here is how you can create DAG in Exchange 2019 running on Windows 2019 core.
First you need to do little planning for DAG. For e.g. what will be dag name, IP and which exchange server will be part of DAG. Once you are ready then run below to create new DAG:-
New-databaseavailabilitygroup -Name mydag -witnessserver cas1 -witnessdirectory C:\DAGwitness -databaseavailabilitygroupaddresses 192.168.100.15
Please take note that witness server can’t be Exchange server which is going to be part of DAG. Also dag can be IP less so you don’t need to provide IP Address like above.
On witness server you have to make exchange trusted group member of administrators group else witness directory will not create and you will get errors when you add members to dag.
After creating dag you can run below command to check if dag is created properly with provided settings:-
get-databaseavailabilitygroup | fl
Once you confirmed that dag is created properly you can go ahead with member addition.
To do so run below:-
Add-databaseavailbilitygroupserver -identity mydag -mailboxserver ex1
To add another server
Add-databaseavailabilitygroupserver -identity mydag -mailboxserver ex2