EMC DL3D 1500 Administrator's Manual page 58

Configuring and Managing Virtual Tape Libraries
Create a single library with many tape drives, but assign only a
few tape drives to each backup server. In this configuration, each
backup server has its own dedicated resources. This also
simplifies the initial installation and avoids any driver-related
issues you may encounter when sharing a tape device between
different OS platforms.
58 EMC DL3D 1500 and DL3D 3000 Administrator's Guide