HSG80 ACS Solution Software V8.6 for SGI IRIX Installation and Configuration Guide

1–16 HSG80 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 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_CONTROLLER/OTHER_CONTROLLER command
determines how the 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 Host Connection Offsets and Unit Numbers 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.
It is recommended to use the following conventions 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).