HP StorageWorks 1900ux User Manual page 25

Operations
Some of the front panel tests will work differently and have different initial
requirements in a mixed media unit. For example, the DRIVE IO test will
require disks of both types in the unit and will only be able to load disks into
drives of the same type.
MO drives can only accept a SCSI address from 0 to 7.
HP StorageWorks 1000ux/1900ux/2300ux Optical Jukebox User's Guide 25