Compaq StorageWorks HSG60 ACS Solution V8.6 for SGI IRIX Installation and Configuration Guide

1–16 HSG60 ACS Solution Software Version 8.6 for SGI Irix Installation and Configuration Guide
An additional factor to consider when assigning unit numbers and offsets is SCSI version.
If the SCSI_VERSION switch of the SET this_controller/other_controller command is set
to SCSI-3, the Command Console LUN (CCL) is presented as LUN 0 to every connection,
superseding any unit assignments. The interaction between SCSI version and unit
numbers is explained further in the next section.
In addition, the access path to the host connection must be enabled for the connection to
access the unit. See “Restricting Host Access in Transparent Failover Mode,” page 1–17.
Assigning Unit Numbers Depending on SCSI_VERSION
The SCSI_VERSION switch of the SET THIS/OTHER CONTROLLER command
determines how the Command Console LUN (CCL) is presented. There are two choices:
SCSI-2 and SCSI-3. The choice for SCSI_VERSION affects how certain unit numbers and
certain host connection offsets interact.
Assigning Unit Numbers and Host Connections in SCSI-2
Mode
Some operating systems expect or require a disk unit to be at LUN 0. In this case, it is
necessary to specify SCSI-2 mode.
If SCSI_VERSION is set to SCSI-2 mode, the CCL floats, moving to the first available
LUN location, depending on the configuration.Because the SWCC Agent depends on the
exact location of the CCL, keep the CCL at LUN 0 by assigning units starting with D1 or
D101. The following conventions are recommended when assigning host connection
offsets and unit numbers in SCSI-2 mode:
■ Offsets should be divisible by 10 (for consistency and simplicity).
■ Unit numbers should be assigned at connection offsets (so that every host connection
has a unit presented at LUN 0).
Table 1–1 summarizes the recommendations for unit assignments based on the
SCSI_VERSION switch.
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