There was an option... "RAIDirector", but I guess is not available since 8.6.
"RAIDirector®
RAIDirector is a tape RAID option, supporting RAID levels 0, 1, 0+1 and 3, that provides increased performance and fault tolerance of existing tape hardware while dramatically shrinking the backup window - and for a fraction of the cost of hardware-based solutions. Logically linking multiple independent SCSI tape devices provides flexibility for mirroring (ideal for offsite storage), striping and striping with parity. Also, exclusive RAID stacking allows for mirrored, striped sets. "