Hi!
Few things to check if the drives are not getting detected in Backup Exec....
1. Is the drive or tape library listed in HCL of Backup Exec
Libraries & drive HCL : http://support.veritas.com/docs/271381
Stand alone Drives HCL : http://support.veritas.com/docs/271380
2. If OS is seeing the device, Backup Exec should see it, if it is not need to check the SCSI IDs and IRQs, generate CONFIG.TXT with LOAD CONFIG.NLM and check the TOP OF STORAGE INFORMATION and check if the IRQs used by SCSI Card are conflicting with IRQs of RAID controller, if so resolve the conflict and see the results
Before we troubleshoot this issue further, I request you to check the HCL cause I couldn't find the SONY AIT SDX-450v as tested and listed in both the HCLs, if its not tested with backup exec we can not continue troubleshooting. As its not recommended using incompatible hardware.
Thanks & Regards
Tammali