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10 Handling multiple initiators
Several Fibre Channel devices may initiate commands through the FibreBridge to SCSI devices. The
basic mechanism to resolve possible conflicts among initiators is to use SCSI Reserve and Release
commands.
A Fibre Channel host in your SAN may need
exclusive access to a SCSI device. SCSI Reserve
and Release commands allow logical units to be
reserved or released under host control.
The FibreBridge intercepts any Reserve or
Release command from a Fibre Channel host,
performs initial processing and, if appropriate,
relays the Reserve command to the SCSI device.
In relaying the Reserve or Release command, the
absolute identity of the host initiator is lost.
Initiators on both the Fibre Channel (via the
FibreBridge), and on the SCSI bus may initiate
commands to the SCSI devices.
1 The FibreBridge receives a SCSI
Reserve command.
Tier 1
2 The FibreBridge determines, via its
internal database, whether there are
conflicting concurrent reservations for
the target SCSI device.
Exhibit 10.0-1 Example 1: A single initiator presents no conflicts: a single initiator is attached to one or more
FibreBridge devices. One initiator is located on the FC-AL and no other initiators reside on the SCSI bus.
1. A single Fibre Channel initiator sends the
FibreBridge.
2. The FibreBridge determines that no reservation conflict exists at Tier 1.
3. The FibreBridge sends the Reserve command to the SCSI target.
4. The SCSI target is reserved until a
FC Initiator 1
39
ATTO Technology FibreBridge 2300E/R/D Installation and Operation Manual
Single Initiator
Release command is sent.
Fibre Channel
Arbitrated Loop or
Fabric
3 If there is a conflict, the FibreBridge
returns a check condition with
Reservation Conflict to the Initiator. If
there is no conflict, the FibreBridge
marks the SCSI device as Reserved in its
internal database.
Tier 2
4 The FibreBridge relays the Reserve
command to the SCSI device.
5 The SCSI device determines whether it is
already reserved.
6 If the SCSI device is reserved, it returns
a Reservation Conflict to the FibreBridge.
The FibreBridge removes its reserved
indicator, and returns Reservation Conflict
to the Initiator. If the SCSI device was not
previously reserved, the SCSI device is
reserved and returns success to the
FibreBridge. The FibreBridge then
returns success to the initiator.
The FibreBridge does not implement extent
reservation.
Reserve command through the FC-AL to the
ATTO FibreBridge 1
SCSI target
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