Rebalance databases in a DAG on Exchange 2010

Sometime you will find that your mailbox database will all be mounted on one of your mail servers where they should be split between members of your DAG. This can be caused but network outages, server crashes and more.

Microsoft have included a powershell script that you can run to quickly fix this. By running this script with the options below, Exchange will attempt to put all mailbox databases back on their preferred servers based on Activation Preference.

From an exchange server, launch the Exchange Management Shell

1. cd "C:\Program Files\Microsoft\Exchange Server\V14\Scripts"

2. .\RedistributeActiveDatabases.ps1 -DagName nameofyourdag -BalanceDbsByActivationPreference

3. For each mailbox that it says Considering move of 'DATABASE NAME' from 'SERVER' to 'SERVER' type Y and press enter. There is an option to say yes to all but i've never had any success out of it.

4. When its finished, open the exchange management console and check the screen above. It should show half mounted on one and half on the other.

If you get a message come up saying that a move has failed because the content index state is failed you will need to run the following command in the exchange management shell on the server which the content state is failed on.

Update-MailboxDatabaseCopy "MAILBOX_DATABASE_NAME\SERVER_NAME" -CatalogOnly