User`s guide

1.5.3 Host Storage Addressing (HSZ Array Controllers)
Figure 1–4 shows a typical connection between an HSZ array controller and
its host. In this case, the SCSI–2 host device interface consists of device ports
(buses), each connected to a SCSI–2 bus containing up to eight devices. The HSZ
array controller resides on one of the SCSI–2 buses. A single HSZ array controller
can be assigned up to four SCSI target IDs on the bus (a dual-redundant pair also
can have up to four SCSI target IDs between them; they share the same four).
Figure 1–4 Host Storage Addressing (HSZ40 Array Controllers)
CONTROLLER
PORT
N
SCSI
BUS N
PORT
1
HOST
PORT
ADDRESS
HOST
TARGET
ADDRESS
HOST
LUN
ADDRESS
LUN
0
LUN
1
LUN
2
LUN
3
LUN
4
LUN
5
LUN
6
LUN
7
SCSI
BUS 1
CXO-4107A-MC
DEVICE INTERFACE
HOST INTERFACE
(VIRTUAL DEVICES)
HOST
SCSI ID x
A SCSI host also sees host logical units through the controller. However, in
SCSI systems, there can be only up to eight units per ID. For the HSZ array
controller, this translates as a maximum of 32 units, or eight per each ID. The
host addresses each logical unit by a SCSI logical unit number, also called a LUN.
Note
Although they share the same name, controller LUNs and SCSI
host LUNs are logical addresses for two different storage structures.
Controller LUNs exist only on the controller’s device interface, and SCSI
host LUNs exist only on a SCSI host’s device interface.
Introduction to HS Array Controllers 1–11