I have a fresh install of Exchange 2007 SP1 RU10 on a Server 2008 box that I am setting up to be the target of an SCR cluster. That will be its only purpose and it will not host any other roles. I have not configured SCR yet. When I deleted the default storage group that was created by the Exchange installation, then rebooted, the MSEXCHANGEIS service failed to start. I created a new (empty) SG, rebooted, and the service started just fine. My question is: do I have to have at least 1 SG, and if so, why?

Databases are stored in SG, you need the SG to hold the databases. as you are creating an SCR Target which has to be a mailbox server ( it will be holding your replicated db). - hope it helps.

Yes, you need at least one storage group (SG). An Exchange SG is a logical container for Exchange databases and their associated system and transaction log files. In high availability scenarios (CCR, LCR and SCR), an SG can only contain a single database and its system and log files. That made the concept obsolete, and it's dropped in Exchange 2010. Exchange 2007 Store Related Changes and Improvements http://www.msexchange.org/tutorials/Exchange-2007-Store-Related-Changes-Improvements.html Uncovering Exchange 2010 Database Availability Groups (DAGs) (Part 1) http://www.msexchange.org/articles_tutorials/exchange-server-2010/high-availability-recovery/uncovering-exchange-2010-database-availability-groups-dags-part1.htmlMCTS: Messaging | MCSE: S+M | Small Business Specialist