When installing Netvault for first time we were seing that Netvault detects 2 tape libraries and 4 drives when adding it for first time.
Netvault shows 4 drives as the following
3-0.0 IBM ULT3580
3-0.1 IBM ULT3580
4-.0.0 IBM ULT3580
4-.0.1 IBM ULT3580
But there are just two real drives.
You can see that it is seeing the same drive twice, because the serial number is the same. The device address is different, meaning that there are two connections from the NVBU server to the drive. This means you have 2 fiber connections from the NVBU server to a fiber switch. This is multi pathing and is not supported by NVBU.
Unplug one of the fiber connections on the Netvault server, You will then start seeing the real number of drives and ready to add it to Netvault.