Not familar with EMC Ionix but I assume it allows you to execute commands remotely. If you post the output of ioscan -k here we may be able to determine if OS is seeing drives. (omitting any info that is propriitary to your company) Also can you confirm the following
1.) Are the tape drive in question attached to this HP-UX MediaAgent?
2.) What type of drives are they? (eg.. Ultrium, DLT)
3.) Does this MediaAgent control the arm of the library
4.) Output of ioscan -k
If problem persists, you might want to contact the Unix Admin of this machine or HP as they can also help get drive detected.
CommVault, Business Critical Support