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

Table Of Contents
Planning a Subsystem
1–8 HSG80 ACS Solution Software Version 8.7 for Compaq Tru64 UNIX Installation and
Configuration Guide
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.
In multiple-bus failover mode, you can specify which units are normally serviced by a
specific controller of a controller pair. Units can be preferred to one controller or the
other by the PREFERRED_PATH switch of the
ADD UNIT (or SET unit) command. For
example, use the following command to prefer unit D101 to “this controller”:
SET D101 PREFERRED_PATH=THIS_CONTROLLER
NOTE: This is an initial preference, which can be overridden by the hosts.
Keep the following points in mind when configuring controllers for multiple-bus
failover:
Multiple-bus failover can compensate for a failure in any of the following:
Controller
Switch or hub
Fibre Channel link
Host Fibre Channel adapter
A host can redistribute the I/O load between the controllers
All hosts must have operating system software that supports multiple-bus failover
mode