Installing Exchange 2010 mailbox role creates a mailbox database by default and gives a random name. I am sure everyone will agree that this brings more pain than any benefit. It would have been nice if there was a section to provide the default database name in the setup wizard. Once the mailbox role is installed, an admin has to either change the name of the database to follow the naming conventions of the company and move the database to the correct LUNs or create a new database, move all mailboxes (including arbitration ones) and delete the database created as part of the setup. I have explained here how to deal with the default database.
Another efficient method of dealing with this problem is to run the Exchange 2010 installation from the command line. The Setup.Com includes switches to better manage the creation of the default database. Though you can’t block the setup from creating the default database, you can give a database name (which follows your naming convention) and the setup will create the default database with that name.
Run the command below (assuming that you are in the Exchange 2010 installation source directory) to create a default database called DB1.
Setup.Com /mode:install /roles:mailbox /InstallWindowsComponents /MdbName:DB1
You can specify the path for the default database as well. That way, you can move the database & log files to the appropriate LUN as part of the setup. Run the following command to have the database in drive “D” and logs in “L”.
Setup.Com /mode:install /roles:mailbox /InstallWindowsComponents /MdbName:DB1 /Dbfilepath:D:DatabasesDB1DB1.edb /Logfolderpath:L:LogsDB1
If you want to install Exchange 2010 in a different drive that the system one, say drive “E”, run the command below.
Setup.Com /mode:install /roles:mailbox /InstallWindowsComponents /TargetDir:”E:Program FilesMicrosoftExchange ServerV14” /MdbName:DB1 /Dbfilepath:D:DatabasesDB1DB1.edb /Logfolderpath:L:LogsDB1
Check TechNet for the full switches that can be used with Setup.Com
No more messing around with the default database 
