In Exchange Server 2000 until Exchange Server 2007 there were Storage Groups. A Storage Group is a grouping of one or more Mailbox Databases (up to five Databases in one Storage Group) combined with a set of Log Files and a Checkpoint File. Pages from memory are handled in memory of the Exchange Server and stored as transactions in the Log Files. Later on the transactions are stored in the Database file and the Checkpoint File keeps track of which transactions are stored in the Database and which are still in the Log Files (but not yet in the Database).
When using a replication mechanism in Exchange Server 2007, whether it be Local Continuous Replication (LCR), Cluster Continuous Replication (CCR) or Stand-by Continuous Replication (SCR) the use of only one Mailbox Database per Storage Group is enforced.
In Exchange Server 2010 Microsoft removed the Storage Groups, but the principle of the transactional usage with the Database, the Log Files and the Checkpoint File is still the same.
All commands with respect to the Storage Groups have been removed, but in the Exchange Management Console as well as the Exchange Management Shell.
For example, to create a new Mailbox Database you would open an Exchange Management Shell and enter the following command:
New-MailboxDatabase –Name DB02 –Server MBXSERVER –EdbFilePath G:\DB02\DB02.log –LogFolderPath G:\Log02