cfgmgr does not configure more than 8 LUNs on OEM RAID
OEM RAID device, Fast/Wide SCSI adapter
Customer has an OEM RAID device with 28 logical units (LUNs)
divided between two systems. When he runs cfgmgr, only the first
8 of the 14 LUNs assigned to the system show up. Customer can
manually configure the other 6 LUNs as "Other SCSI Disk Drive"
using the mkdev command. Since AIX supports 32 LUNs per SCSI
address, why is cfgmgr only configuring the first 8?
The SCSI-2 standard specifies that up to 8 LUNs may be supported
at a given SCSI ID. Some vendors have developed support for LUNs
beyond 7 for their devices. These are typically RAID devices.
AIX will check the ANSI level in the inquiry data for all disks.
If the ANSI level is SCSI-1 or SCSI-2, then AIX will only attempt
to configure LUNs from 0 to 7. If the disk were to report an
ANSI level of SCSI-3, then AIX will attempt to configure LUNs
from 0 to 31.
The reason this is necessary is that 32 LUNs per SCSI address is
not supported by the SCSI-2 standard and the operating system
would be in violation of that standard if it were to attempt to
identify LUNs beyond 7. There has been reported instances where
SCSI-2 devices will respond at LUN 8 as if it were LUN 0
(ignoring the high order bits of the LUN), or will hang the SCSI
bus when going beyond LUN 7.
The SCSI adapter configuration method will never automatically
configure LUNs beyond 7 for any device which identifies itself
Manually configure LUNs beyond 7 using the long form of the
mkdev command or SMIT. To ensure that these LUNs are available
after reboot of the system, write a script with the mkdev -l
commands, and create an entry in the /etc/inittab script which
calls the script.
For example, if the script is called "raid.add", and is located
in the /usr/local/bin directory, the /etc/inittab entry should
Support Line: cfgmgr does not configure more than 8 LUNs on OEM RAID ITEM: DB6596L
Dated: August 1997 Category: N/A
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