HP Array Controller HSG V8.7 Software - Manual (Page 107)

Creating Storagesets 3–29
Assigning Unit Numbers in Multiple Bus Failover Mode
In multiple bus failover mode, the range of assignable units, which are
accessible from any port on the subsystem, is 0-199. Hosts obtain units
by reserving the unit for sole access. This is done on a first-available
basis. Figure 3–11 illustrates the controller port ID and unit numbers in
multiple bus failover mode.
Figure 3–11 Controller Port ID Numbers and Unit Numbers in
Mulitple Bus Failover Mode
Assigning Unit Offsets
Unit offsets are used to define the first unit number that a host is able to
access on the controller. When assigning unit offsets, keep in mind that
the unit offset is settable on a per-host basis. Thus, one host can have a
unit offset of 0 and see units 0-99 as LUNs 0-99, and another host can
have a unit offset of 10 and see units 10-99 as LUNs 0-89 (controller
unit number 10 is seen at the host as LUN 0). This is useful for hosts
that have a limited LUN addressing range.
Figure 3–12 depicts the use of unit offsets on a per-host basis. Note that
controller units 0-99 are presented only on Port 1, and units 100-199
are presented only on Port 2. This implies that Port 1 hosts can have a
unit offset range of 0-99, and Port 2 hosts can have a unit offset range
of 100-199.
Controller A
Port 1 (Primary)
Units 0-199
Port 2 (Primary)
Units 0-199
Controller B
Port 1 (Primary)
Units 0-199
Port 2 (Primary)
Units 0-199
CXO6454A