When adding a drive to the Data Domain box, you couldn’t see that drive in the emulated tape library (ETL) within NetVault Device Management whilst modifying it.
Even restarting the NetVault Services didn’t resolve the issue.
Perform the following steps to resolve the issue:
1] Add the drive(s) in Data Domain on the VTL Management section.
2] Stop the NetVault services in the NetVault Server Configurator > Services tab.
3] Modify the Access Groups in Data Domain.
4] Restart NetVault Server services.
5] Modify the ETL to add the drive(s) and make sure that the drives are all added in the correct order (compare the drive serial number in the NetVault drive and Data Domain configurations).
Then perform some backups to test all the drives.