Compaq StorageWorks HSG60 ACS Solution Software V8.6 for Linux X86 and Alpha Installation and Configuration Guide

1–16 HSG60 ACS Solution Software Version 8.6 for Linux X86 and Alpha 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 1–18.
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.
IMPORTANT: SCSI-
Assigning Unit Numbers and Host Connections in SCSI-3
Mode
If SCSI_VERSION is set to SCSI-3, the CCL is presented as LUN 0 to all connections. The
CCL supersedes any other unit assignment. Therefore, in SCSI-3 mode, a unit that would
normally be presented to a connection as LUN 0 is not visible to that connection at all.
The following are recommendations for assigning host connection offsets and unit
numbers in SCSI-3 mode:
■ Offsets should be divisible by 10 (for consistency and simplicity).
■ Unit numbers should not be assigned at connection offsets (to avoid being masked by
the CCL at LUN 0).
For example, if a host connection has an offset of 20 and SCSI-3 mode is selected, the
connection will see LUNs as follows:
LUN 0 - CCL
LUN 1 - unit 21
LUN 2 - unit 22, etc.