HSG80 ACS Solution Software Version 8.7 for Compaq Tru64 UNIX Installation and Configuration Guide

Planning a Subsystem
1–6 HSG80 ACS Solution Software Version 8.7 for Compaq Tru64 UNIX Installation and
Configuration Guide
enabling the standby port to take over for the active one. If one controller fails, its
companion controller (known as the surviving controller) takes control by making
both its host ports active, as shown in Figure 1–6.
Units are divided between the host ports:
• Units 0-99 are on host port 1 of both controllers (but accessible only through the
active port).
• Units 100-199 are on host port 2 of both controllers (but accessible only through
the active port).
Transparent failover only compensates for a controller failure, and not for failures of
either the Fibre Channel link or host Fibre Channel adapters.
Figure 1–5: Transparent failover—normal operation
CXO7036A
Host
port 1
active
Host
port 2
active
D100 D101 D120D0 D1
Host 1
Switch or hub
Host 2
Switch or hub
Host 3
Controller A
Controller B
Host
port 2
standby
Host
port 1
standby