Upgrade Exchange Server 2016 DAG to 2019

Occasional Contributor

We are currently planning the upgrade of our Exchange Server 2016 DAG (on Windows Server 2012 R2) to Exchange Server 2019. I have found it surprising that there are a fair number of articles about migrating from 2010 or 2013, but very few resources for our current scenario. Is the only option to stand up a new DAG and use ECP to move mailboxes (or databases) to the new DAG? Can anyone point me to documentation about how to manage namespaces, load balancers, and clients during this transition?



4 Replies

@Sam Erde 


Give the Exchange Deployment Assistant a look.


This will probably answer most of your questions.

@Michael_Larrivee, the Exchange Deployment Assistant is a fantastic resource. I did go through it already, with two significant questions remaining unanswered. 


First, it doesn't speak about DAGs. Perhaps there is assumed knowledge that moving mailboxes from 2016 to 2019 can happen in the same manner regardless of having a DAG or no DAG. This is where my lack of experience comes into play and I was hoping for a clear answer. What kind of separation happens for an organization that has more than one DAG? Is a DAG simply considered a replication boundary, but otherwise able to to share full organization functionality such as address lists, policies, receive connectors, and namespace? 


Second, can multiple DAGs share the same namespace and load balancing topology? Meaning: for a migration from 2016 to 2019, can we build a new 2019 DAG, configure it to use the same namespace/URLs, and then add these 2019 nodes to our current load balancers alongside the 2016 servers? 


My gut optimistically suggests that the answer to this second question is "yes," but we're just looking for documented confirmation of that before beginning. 


Thanks again!

best response confirmed by Sam Erde (Occasional Contributor)

@Sam Erde


Yes, a dag is a replication boundary and moving mailboxes to 2019 dag is no different than moving mailboxes from exchange server to exchange server.  It can share the same name space as your 2016 dag and you are correct, you would add the 2019 nodes to the load balancer when you are comfortable.  What I would do is go through the 2016 virtual directory settings and mirror them on the 2019 servers.  Make sure you have any certificates installed on the 2019 server.  You'll have to update your send connectors to include your 2019 servers as necessary and mirror the 2016 receive connectors and their settings on your 2019 servers.

@Michael_Larrivee, thank you. Makes perfect sense. Just wish I could have found some documentation that explicitly noted "these steps also work with a DAG" and "a load balanced namespace" so I could assuage concerns from the change advisory board.