Tape devices are as large as your budget. Today from 3GB to thousands of TB.
For the mid-priced SCSI device range from DAT 4GB to DLT 360GB tapes. There are other solutions with higher per tape capacity and of course prices.
With autoloaders and robotic libraries, start the multiplication.
Example: I reciently upgraded from a single DLT VS80 (advertized 80GB, averaged 60GB) to an autoloader DLT VS80 for 8 tapes so is called a DLT VS640 (advertized 640GB, expecting 480GB or less).
Andy