HSG80 ACS Solution Software V8.6 for Windows NT and Windows 2000 Installation and Configuration Guide

Planning a Subsystem 1–17
Figure 1–11. Connections in multiple-bus failover mode
Assigning Unit Numbers
The controller keeps track of the unit with the unit number. The unit number can be from
0−199 prefixed by a D, which stands for disk drive. A unit can be presented as different
LUNs to different connections. The interaction of a unit and a connection is determined by
several factors:
■ Failover mode of the controller pair
■ The ENABLE_ACCESS_PATH and PREFERRED_PATH switches in the ADD UNIT (or
SET unit) commands
CXO7080B
Host
port 1
active
Host
port 2
active
Host
port 2
active
Host
port 1
active
D100 D101 D120D0 D1 D2
Controller A
Controller B
All units visible to all ports
Switch
or hub
Switch
or hub
NOTE: FCA = Fibre Channel Adapter
Host 1
"VIOLET"
FCA1 FCA2
Connection
VIOLET1B1
Connection
VIOLET1A1
Connection
VIOLET2A2
Connection
VIOLET2B2