When you install Backup Exec, support for the first drive in every robotic library is included. The Library Expansion Option enables support for each additional drive in a robotic library.
To install the Library Expansion Option, add a license.
You can find a list of compatible types of storage in the Backup Exec Hardware Compatibility List:
You can find license information for the Library Expansion Option in the Backup Exec Customer Pricing and Licensing Guide: