IBM Netfinity 3500, User Handbook Manual

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If you install wide (16-bit) SCSI devices, you can set the IDs to any
whole number between 0 and 6, or between 8 and 15. If you install
narrow (8-bit) SCSI devices, you can set the IDs to any whole
number between 0 and 6.
SCSI Logical Unit Number
Each physical device has a physical unit number (PUN) and a
logical unit number (LUN). If a physical device supports no logical
devices, its LUN is 0. Most SCSI devices support only LUN 0.
Certain types of physical SCSI devices (bridge controllers) can support
more than one logical device.
For example, a printer controller might support up to eight printers.
The printer controller is a physical device, and each printer is a
logical device. If the printer controller is assigned to ID 2, the ID of
the first printer appears in the SCSI device configuration as PUN 2,
LUN 0. The IDs of the other printers are PUN 2, LUN 1; PUN 2,
LUN 2; on up to PUN 2, LUN 7.
Termination Requirements
All Netfinity 3500 servers come with an UltraSCSI controller on the
system board. This UltraSCSI controller provides termination for
one end of the SCSI bus (cable) in your server. However, the SCSI
bus must be terminated at both ends only. Any SCSI devices that
are installed must have their termination set to Disabled.
Ÿ
When you install devices in bays 2, 3, 5, and 6, you must disable
the termination for the devices before you install them.
Ÿ
If you connected external SCSI devices to your server, set the
termination for the last device on the external cable to Enabled.
See the device documentation for instructions.
Refer to the instructions that come with the SCSI device for more
information about termination.
Chapter 4. Installing Options
75