Best Practice for Exchange 2010 journal mailboxes

Hi Guys,

Trying to understand what the best practice is for Exch. 2010 journal mailboxes.

Customer has 4 Exch. 2010 DAG-ed servers (Exch.1, 2, 3, 4) and 4 journal mailboxes.  They are doing journaling ONLY.  No mailbox archiving.

They have put all 4 journal mailboxes on a single Exchange server (Exch.4) and they have added Exch.4 server to the Exchange Server Targets container in EV.  Exch. 1, 2, 3 are NOT added.

QUESTIONS:

1. If one of the journal mailboxes fails over to any of the other 3 Exchange servers via DAG failover, will journaling continue to work? 

2. Do they need to add Exch.1,2,3 to the Targets container for point 1 above to work?

3. Anything else they need to do?

Thanks,