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

Planning a Subsystem 1–7
Figure 1–6. Transparent failover—after failover from controller B to controller A
Multiple-Bus Failover Mode
Multiple-bus failover mode has the following characteristics:
■ Host controls the failover process by moving the unit(s) from one controller to another
■ All units (0 through 199) are visible at all host ports
■ Each host has two or more paths to the units
All hosts must have operating system software that supports multiple-bus failover mode.
With this software, the host sees the same units visible through two (or more) paths. When
one path fails, the host can issue commands to move the units from one path to another. A
typical multiple-bus failover configuration is shown in Figure 1–7.
CXO7035A
Host
port 1
active
Host
port 2
active
D100 D101 D120D0 D1
Host 1
Switch or hub
Host 2
Switch or hub
Host 3
Host
port 1
not
available
Controller A
Controller B
not available
Host
port 2
not
available