HSG80 ACS Solution Software V8.6 for Windows NT and Windows 2000 Installation and Configuration Guide

Planning a Subsystem 1–21
Assigning Host Connection Offsets and Unit Numbers 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 methods are recommended 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.
In this example, if a unit 20 is defined, it will be superseded by the CCL and invisible to
the connection.
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.
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).