Exchange 2013 EAC Batch Mailbox Move Generates Large Number Of Transaction Log Files

You will be in for a surprise when you run a batch move to migrate mailboxes from legacy Exchange versions to 2013, as the transaction log files starts growing at a faster rate and even fills up the disk!

Now the fact that will surprise you even more is that the database that is getting filled with all the log files may not even be the source or target for the mailbox move. So, what is going on here?

In Exchange 2013, the batch mailbox move with the EAC and the *-MigrationBatch cmdlet uses the “Migration.8f3e7716-2011-43e4-96b1-aba62d229136” arbitration mailbox to store the metadata such as batches and migration user information. If you are moving a batch of big mailboxes, large number of transaction logs will be generated in the mailbox database that hosts “Migration.8f3e7716-2011-43e4-96b1-aba62d229136” arbitration mailbox.

This log generation is by design and cannot be changed. There are a few workarounds which you can implement.

1. Enable circular logging for the database that hosts the “Migration.8f3e7716-2011-43e4-96b1-aba62d229136” arbitration mailbox. This is the default database that gets created as part of the 2013 setup (by default). You can have this database running with just the arbitration mailboxes. The database should be dismounted and mounted back after enabling circular logging.

2. Increase the volume size for the database that hosts the arbitration mailbox, keep an eye on it and run backups everyday to flush the logs.

3. Use the New-MoveRequest to move the mailboxes instead of the batch move in EAC or the *-MigrationBatch cmdlet. The New-MoveRequest cmdlet doesn’t use the arbitration mailbox and works identical to the 2010 mailbox move. You will not have the new features in the 2013 batch move though (like enhanced reporting).

In short, choose one of the workarounds if you want to use the new batch mailbox move in Exchange 2013 ;)