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

Planning a Subsystem 1–25
For example:
In Figure 1–13, assume both host connections on port 2 (connections BLACK1B2 and
BROWN1B2) initially have the default port 2 offset of 100. Setting the offset of
connection BROWN1B2 to 120 will present unit D120 to host BROWN as LUN 0.
SET BROWN1B2 UNIT_OFFSET=120
Host BROWN cannot see units lower than its offset, so it cannot access units D100 and
D101. However, host BLACK can still access D120 as LUN 20 if the operating system
permits. To restrict access of D120 to only host BROWN, enable only host BROWN’s
access, as follows:
SET D120 DISABLE_ACCESS_PATH=ALL
SET D120 ENABLE_ACCESS_PATH=
BROWN1B2
NOTE: Compaq recommends that you provide access to only specific connections, even if there
is just one connection on the link. This way, if new connections are added, they will not have
automatic access to all units.
Restricting Host Access in Multiple-Bus Failover Mode
In multiple-bus mode, the units assigned to any port are visible to all ports. There are two
ways to limit host access in multiple-bus failover mode:
■ Enabling the access path of selected host connections
■ Setting offsets
Enablign the Access Path of Selected Host Connections
Host access can be limited by enabling the access of certain host connections and
disabling the access of others. This is done through the ENABLE_ACCESS_PATH and
DISABLE_ACCESS_PATH switches of the
ADD UNIT (or SET unit) commands. Access path is
a unit switch, meaning it must be specified for each unit. Default access means that the
unit is accessible to all hosts. It is important to remember that at least two paths between
the unit and the host must be enabled in order for multiple-bus failover to work.