If there is one area of Exchange 2010 that was poorly documented and poorly understood it has to be database maintenance.  The problem stemmed from the significant changes that we made in the store for Exchange 2010 and a confusion of terms. This has led many people in the field to get confused about what is actually going on in the various database maintenance activities.

Well.. I am pleased to say that Ross Smith IV has written a fantastic article that explains what is actually going on inside these mystical processes and what they actually do for us…

http://blogs.technet.com/b/exchange/archive/2011/12/14/database-maintenance-in-exchange-2010.aspx