Maxtor ATLAS 10K III - Manual (Page 220)

SCSI Description
5-156 Maxtor Atlas 10K III
 4'5'48'  %QOOCPF J
The RESERVE and the RELEASE commands are used for contention resolution in
multiple-initiator systems. The RESERVE command is used to reserve a logical unit.
If RESERVE (10) is used, then RELEASE (10) is also used. The data format and the
field descriptions are described in Table 5-188 and Table 5-189 respectively. The data
format for the Event Descriptors is described in Table 5-190.
Table 5-188 RESERVE (10) Command Descriptor Block-Data Format
Table 5-189 RESERVE (10) Command-Field Descriptions
$KV
$[VG
       
0 Operation Code (56h)
1 Reserved 3rdPty Reserved LongID Extent
2 Reservation Identification
3 Third Party Device ID
4 - 6 Reserved
7 - 8
(MSB)
Parameter List Length
(LSB)
9 Control
(KGNF &GUETKRVKQP
3rd Pty When set to 1, it indicates that the Third Party Device ID field is valid.
LongID
When 0, indicates that the third party device associated with the reservation release
has a number smaller than 255 and the ID value can be sent within the CDB. If set
= 1, indicates that the third party device ID is greater than 255, the ID value within
the CDB is ignored, and the parameter list length is at least eight.
Third Party
Device ID
Required and used only when the 3rdPty bit is set, in which case this field specifies
the SCSI ID of the initiator to be granted the reservation of the logical unit. The drive
preserves the reservation until one of the following occurs:
• It is superseded by another valid RESERVE command from the initiator.
• It is released by the same initiator.
• It is released by a TARGET RESET message from any initiator.
• It is released by a hard reset condition.
The drive ignores any attempt to release the reservation made by any other initiator.
For example, if ID7 sends ID2 a Third Party reservation on behalf of ID6 (the target
at ID2 gets reserved for the initiator ID6), then only ID7 can release the target at ID2
(using a Third Party release). ID6 cannot release the reservation even though the res-
ervation was made on its behalf.
Extent
If 0, requests that the entire logical unit be reserved for use only by the initiator until
the request is supplanted by another valid RESERVE command from the same initia-
tor, or until released via a RELEASE (10) command from the reserving initiator, a hard
reset, or a power on cycle.
If set = 1, the extent reservation option is implemented. This option allows an ap-
plication client in a multitasking environment to have multiple reservations.
The size of the extent list is defined by the contents of the Parameter List Length
field. The extent list consists of zero or more descriptors. Each descriptor defines an
extent beginning at the specified logical block address for the specified number of
blocks. If the number of blocks is 0, the extent begins at the specified logical block
address and continues through the last logical block address on the logical unit. The
data format of extent descriptors is shown in Table 5-190.