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

Table Of Contents
Planning a Subsystem
1–21HSG80 ACS Solution Software Version 8.7 for Compaq Tru64 UNIX Installation and
Configuration Guide
1–21
What is Selective Storage Presentation?
Selective Storage presentation is a feature of the HSG80 controller that enables the
user to control the allocation of storage space and shared access to storage across
multiple hosts. This is also known as Restricting Host Access.
In a subsystem that is attached to more than one host or if the hosts have more than
one adapter, it is possible to reserve certain units for the exclusive use of certain host
connections.
For a controller pair, the method used to restrict host access depends on whether the
controllers are in transparent or multiple-bus failover mode. For a single controller, the
methods are the same as for a controller pair in transparent failover.
NOTE: The default condition is ENABLE_ACCESS_PATH=ALL. This specifies that access
paths to ALL hosts are enabled. StorageWorks recommends that the user restrict host access
and that the access path be carefully specified to avoid providing undesired host connections
access to the unit.
Restricting Host Access in Transparent Failover Mode
Three methods can be used to restrict host access to storage units in transparent
failover mode:
Using separate Fibre Channel links (either loop or fabric)
Enabling the access path of selected host connections on a shared loop or fabric
Setting offsets
NOTE: These techniques also work for a single controller.
Table 1–1: Unit Assignments and SCSI_VERSION
SCSI_VERSI
ON
Offset
Unit
Assignment
What the connection sees
LUN 0 as
SCSI-2 Divisible by
10
At offsets Unit whose number
matches offset
SCSI-3 Divisible by
10
Not at offsets CCL