Hello Rajnish,
RSM is used by Windows mainly to store the storage devices and media related information, when you are using the Windows native backup utility (NTBackup) for backup purpose. For further details refer to following technote
http://support.veritas.com/docs/192880
Backup Exec does not use RSM for storing this information. It has its own database for this purpose. It is always recommended to disable RSM for the storage device that is used with Backup Exec. So backing up RSM is not important, as long as you are using Backup Exec.
Hope this helps you.
Regards
NOTE : If we do not receive your reply within two business days, this post would be marked "assumed answered" and would be moved to "answered questions" pool.