Actually, I found the enclosed information on Microsoft's website in tech notes.
http://technet.microsoft.com/en-us/library/aa998926(EXCHG.80).aspx
It seems not possible to rename the store groups but you can add new/delete/move store groups.
[P.S. my migration is going smooth, this forum is wonderful when sharing resources and knowledge.]
Creating a New Storage Group
You can create a new storage group by clicking New Storage Group in the Mailbox node under Server Configuration in the Exchange Management Console. You can also create a new storage group in the Exchange Management Shell with the New-StorageGroup cmdlet. For more information about creating new storage groups, see How to Create a New Storage Group.
Configuring a Storage Group
You can configure many storage group settings by right-clicking a storage group in the work pane of the Mailbox node under Server Configuration in the Exchange Management Console, and then clicking Properties. You can configure all the settings of a storage group in the Exchange Management Shell with the Set-StorageGroup cmdlet.
Removing a Storage Group
You can remove a storage group by right-clicking the storage group in the work pane of the Mailbox node under Server Configuration in the Exchange Management Console, and then clicking Remove. You can also remove a storage group by using the Remove-StorageGroup cmdlet in the Exchange Management Shell. For more information about removing storage groups, see How to Remove a Storage Group.
Moving a Storage Group Path
You can move storage group system and log files by right-clicking the storage group in the work pane of the Mailbox node under Server Configuration in the Exchange Management Console, and then clicking Move Storage Group Path. You can also move the storage group files by using the Move-StorageGroupPath cmdlet in the Exchange Management Shell. For more information about removing storage groups, see How to Move a Storage Group Path.
Managing Databases
You can use both the Exchange Management Console and the Exchange Management Shell to configure options for Exchange mailbox databases and public folder databases. However, the Exchange Management Shell offers access to more information and settings than the Exchange Management Console, and makes available the power of scripting. (For more information about scripting, see Scripting with the Exchange Management Shell and Scripts for Managing Public Folders in the Exchange Management Shell.)
