IBM HANDBOOK 260 - Manual (Page 125)

Storage Architectures and Devices 107
Devices that have two SCSI connectors have internal cabling that must be
included when calculating the total cable length. When attaching these
devices to a SCSI chain, connect one cable to one connector and the other
cable to the other connector. Do not piggy back the second cable/terminator
onto the first as you would with a device that had only one SCSI connector as
shown in Figure 31.
Figure 31. Piggy Back Connectors
A dedicated adapter should be used for attachment of any external enclosure
containing multiple SCSI devices.
4.3.1.3 SCSI Terminators
There must be exactly two terminators on the SCSI bus, and they must be
located at each end of the bus.
• For SCSI adapters with external devices only, make sure the appropriate
SCSI terminator is connected to the last device on the bus.
• For SCSI adapters with internal devices only, make sure that the
appropriate SCSI terminator is connected to the end of the internal SCSI
cable.
• For SCSI adapter with both internal and external devices, make sure the
appropriate SCSI terminator is connected to the last device on the
external bus and that the end of the internal SCSI cable has been properly
terminated.
one connector device two connector device
Use this connector
to attach a cable
or terminator
Single-Ended External Narrow Bus
This "piggy back" connector is
not to be used if it is attached
to a two connector device.