Microsoft Exchange Server 2016 PowerShell Cookbook - Fourth Edition

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The Add-DatabaseAvailabilityGroupServer cmdlet will need to be run for each mailbox server that will be included in the DAG. If you want to automate this process, you have a couple of options.

First, if you simply need to add all of the mailbox servers in the organization to the DAG, use the following command:

    Get-MailboxServer | Add-DatabaseAvailabilityGroupServer DAG  

If you are working in a more complex environment with multiple Active Directory sites, you'll need to do a little more work. When adding servers to a DAG, you'll probably need to limit this to the mailbox servers in a particular Active Directory site. The following code will allow you to accomplish this:

    $mbx = Get-ExchangeServer | ? { `
     $_.Site -match 'Default-First-Site-Name' ...