Compaq StorageWorks HSG60 ACS Solution Software V8.6 for Compaq Tru64 UNIX Installation and Configuration Guide

1–20 HSG60 ACS Solution Software Version 8.6 for Compaq Tru64 UNIX Installation and Configuration Guide
Selective Storage Presentation
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.
Restricting Host Access in Transparent Failover Mode
The following 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.
Restricting Host Access by Separate Links
In transparent failover mode, controller A host port 1 and the controller B host port 1 share
a common Fibre Channel link. Controller A host port 2 and the controller B host port 2
also share a common Fibre Channel link. If the host 1 link is separate from the host 2 link,
the simplest way of limiting host access is to have one host or set of hosts on the port 1
link, and another host or set of hosts on the port 2 link. Each host can then see only units
assigned to its respective controller port. This separation of host buses is shown in
Figure 1–11. This method applies only if the host 1 link and host 2 link are separate links.
Table 1–1 Unit Assignments and SCSI_VERSION
SCSI_VERSION Offset Unit Assign-
ment
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