Tuesday, 22 December 2015

Exchange 2016 Database Availability Group (Part 2)


In part 1, we configured the MAPI and REPLICATION networks and we then set up the Database Availability Group.

In this next part, we’ll configure our mailbox databases to be highly available by adding mailbox database copies.

To read other parts in this series go to:

Lab environment

Let’s quickly confirm the mailbox databases that are already set up. To do this, I’m running the command below:

Get-MailboxDatabase | sort Name


We have four mailbox databses: MDB01, MDB02, MDB03 and MDB04 and only a single copy of each mailbox database.

MDB01 and MDB02 are mounted on LITEX01. MDB03 and MDB04 are mounted on LITEX02. We need to create copies so that each mailbox database has a copy on each server.

Add a mailbox database copy

To add a mailbox database copy, we can use the Exchange Admin Center (EAC) or PowerShell.

To add a mailbox database copy using the EAC

Log into the EAC and click on servers in the left pane then click on databases at the top:


Click on a mailbox database, click “…” then click “add database copy”:


Here we’re presented with the add mailbox database copy wizard which prompts us for the mailbox server:


Click on browse and select the mailbox server you want to add a database copy to then click on OK:


Select the activation preference number. In the case of a failover, Exchange will failover the mailbox database to the copy that has the lowest activation preference number, assuming that it is in sync and other checks pass. Here we’ll accept the default and select an activation preference of 2:


Click Save and you should now see that the database is seeded to LITEX02:


Our mailbox database copy is now added:



Repeat these steps for each mailbox database that you want to make highly available.

To add a mailbox database copy using PowerShell

Use this command to add a mailbox database copy for database MDB02 onto mailbox server LITEX02:

Add-MailboxDatabaseCopy -Identity MDB02 -MailboxServer LITEX02


Repeat these steps for each mailbox database that you want to make highly available.

Get mailbox database copies

Once you’ve added all your mailbox database copies, you can confirm the below:

  • The active copies are mounted on the correct servers
  • The passive copies are healthy
  • The copy queue length is 0
  • The replay queue length is 0
  • The Content Index is healthy

To do this, run the Get-MailboxDatabaseCopyStatus command on each server:

Get-MailboxDatabaseCopyStatus –Server litex01 | sort name


Get-MailboxDatabaseCopyStatus –Server litex02 | sort name


Here we see that all our checks come back good.


In this post, we’ve gone through how to set up our mailbox databases as highly available by adding mailbox database copies so we have at least two copies of each mailbox database should a server fail. This concludes our DAG setup. 

For further reading, see this post for useful information on how to troubleshoot and test your DAG. 


  1. Sorry... Its

    Since exchange 2016 creates IP less DAG

  2. Thanks a lot for this , my lab works perfect!!.

  3. Thanks a lot for this , my lab works perfect!!.

  4. Hi, Thanks for the post.
    It seem there is a limit of 5 databases, is there a way to increase this value ?
    Thanks in advanced.

    1. Hi Paco, the limit for for Standard edition of Exchange is 5 databases. The limit for Enterprise edition of Exchange is 100 databases.

  5. 5 databases is the limit for the standard version of Exchange. The enterprise version will have a much higher limit.

  6. please put an article of disaster recovery in case second server dies

  7. Nice article. Will there be any issue while using IP less DAG?