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SCSI Description
5-96 Maxtor Atlas 10K III
The PERSISTENT RESERVATION OUT command is a 10-byte command used
to reserve a logical unit or an extent within a logical unit for the exclusive or shared
use by an initiator. The command is used in conjunction with the PERSISTENT
RESERVATION IN command; it is not used with the RESERVE and RELEASE
commands.
Persistent reservations conflict with reservations made via the RESERVE command.
Initiators that perform PERSISTENT RESERVATION OUT actions are identified
by a reservation key assigned by the application client. The client may use the
PERSISTENT RESERVATION IN command to identify which other initiators
within a system hold conflicting or invalid persistent reservations and use the
PERSISTENT RESERVATION OUT command to preempt those reservations if
necessary.
Note that since persistent reservations are not reset by the TARGET RESET task
management function or other global actions, they can be used to enact device sharing
among multiple initiators. The PERSISTENT RESERVATION OUT and
PERSISTENT RESERVATION IN commands provide the means for resolving
contentions in multiple-initiator systems with multiple port target. By using the
reservation key to identify persistent reservations, it is possible to determine which
ports hold conflicting persistent reservations and to take over such reservations from
failing or “greedy” initiators.
illustrates the format of the PERSISTENT RESERVATION OUT command. Table
5-119 explains the data fields of the command.
PERSISTENT RESERVATION OUT Command Descriptor Block-Data Format
0 Operation Code (5Fh)
1 Reserved Service Action
2 Scope Type
3 - 6 Reserved
7 – 8
(MSB)
Parameter List Length (18h)
(LSB)
9 Control