About SPC-2 SCSI reserve commands
When a device receives an exclusive access type SCSI persistent reservation command, it does not process commands from any other HBA. The device processes commands from another HBA only when the HBA that owns the reservation issues the release command. If an application sends a command to a reserved device, the device fails the command by returning a status of RESERVATION CONFLICT. The only exceptions to this action are several commands that cannot interfere with the reservation, such as Inquiry or Request Sense.
A device stays reserved until one of the following events occurs on the device:
Released by the HBA that reserved it
Released by a TARGET or a LOGICAL UNIT RESET
These resets are protocol-dependent and differ between parallel SCSI and FCP (SCSI on Fibre Channel ). These resets can be issued from any HBA.
Released by Fibre Channel LOGO, PLOGO, PRLI, PRLO, or TPRLO action or failed discovery (link actions)
Power cycled
A negative consequence of SPC-2 SCSI reserve occurs if the HBA that owns the reservation fails. A device stays reserved until the reservation is removed or broken. Only the original HBA can remove the reservation, which means the system must be available. If the HBA that owns the reservation fails, it cannot remove the reservation. Therefore, the reservation must be broken.
To break a reservation, one of the following actions must break the reservation:
SCSI reset
Bus device reset
LUN device reset
Power cycle
Fibre Channel link actions may break reservations
SPC-2 SCSI reserve commands are mandatory for all SCSI-2 and SCSI-3 devices. See the SCSI 2 standard for a detailed description of SCSI reserve command operation and behavior.