Non-IBM disk array
A non-IBM disk array, like a non-IBM disk drive, is of class disk, subclass SCSI, type osdisk (other SCSI disk drive).
A disk array appears to the operating system as a single, rather
large, disk drive. Because a disk array actually contains a number of physical
disk drives, each of which can handle multiple requests, the queue depth for
the disk array device has to be set to a value high enough to allow efficient
use of all of the physical devices. For example, if hdisk7 were an eight-disk
non-IBM disk array, an appropriate change would be as follows:
# chdev -l hdisk7 -a q_type=simple -a queue_depth=24
If the disk array is attached through a SCSI-2 Fast/Wide SCSI adapter bus, it may also be necessary to change the outstanding-request limit for that bus.