ML3 with 3 drives

Hello,

I'm struggling to find any type of answer online or from our Dell team on this. Our customer has an ML3 with 3x LTO8 SAS drives in it. They want to connect that ML3 to one server using SAS HBA. But he's not able to see the other drives, just one (or two if he direct attaches to two of the tape drives with each port of the HBA)

Is there any type of backplane connecting these three LTO8 drives or does he need to actually have one SAS cable connecting each drive to the server?

In other words, can he manage this tape library using just one SAS cable and HBA? If not, would we daisy-chain the three drives together in the back of the library, or do we need to connect each one of the three LTO drives to a separate SAS HBA port on the server?

Thanks