Instruction manual

At the front of a 2104 Model DU3 there are 14 device slots 1. Each slot must contain
either a SCSI disk drive module, or a dummy disk module. Each disk drive module
connects to a backplane which is mounted vertically about halfway between the front
and back of the 2104 Model DU3.
Note: To run I/O at least one SCSI disk drive module must be present in each 2104
Model DU3.
The 14 device slots are divided into two groups of seven slots. Between the two groups
of seven slots there is a SCSI bridge card2. The SCSI bridge card assigns the disk
drive modules to a SCSI bus, in accordance with the setting of the SCSI bus split
switch on the switch card 5.
On the back of the backplane are connectors for two fan-and-power-supply
assemblies3, two SCSI interface cards4, and a switch card5.
The 2104 Model DU3 has either two fan-and-power-supply assemblies or one
fan-and-power-supply assembly and one fan assembly. Either option provides all the
necessary power and cooling for the 2104 Model DU3.
It is better, however, to have two fan-and-power-supply assemblies, rather than one
fan-and-power-supply assembly and one fan assembly, because then the amount of
power required from each power supply is reduced, and, if one power supply fails,
power for the 2104 disk enclosure continues to be supplied by the other power supply.
The SCSI interface cards4 are used to connect host machines to the 2104 Model
DU3. These cards contain logic that provides information about what is happening in
the 2104 Model DU3 and the status of components within it.
The switch card5 contains switches that control which SCSI bus mode is selected,
how the 2104 Model DU3 is supplied with power, and what enclosure services are
enabled. It also contains a rotary switch that sets the ID of the 2104 Model DU3.
Options for configuring a 2104 Model DU3 are described in the Expandable Storage
Plus: 2104 Model DU3 Installation Guide.
4 2104 Models DU3 and TU3 Operator’s Guide