SCSI Description
5-156 Maxtor Atlas 10K III
The RESERVE and the RELEASE commands are used for contention resoluti on in
multiple-in itiator systems. The RESERVE command is used to reserve a logical unit.
If RESERVE (10) is used, then RELEASE (10) is also us ed. The data f ormat and the
field descriptions are described in Table 5-188 and Table 5-189 respectively. The data
format for the Event Descri pt or s is described in Table 5-190.
RESERVE (10) Com mand Descriptor Block-D a ta For m a t
RESERVE (10) Command-Field Descriptions
0 Ope ration Co de (56 h)
1 Reserved 3rdPty Reserved LongID Extent
2 Reservation Identification
3 Third Party Device ID
4 - 6 Re served
7 - 8 (MSB) Parameter List Length (LSB)
9 Control
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 sen t wit hin the CDB. If set
= 1, indi cates that the thir d pa rty devi ce ID is greater than 255, t he ID value within
the CDB is ignored, and the param eter list lengt h is at least eight.
Third Party
Device ID
Requ ired and used only when t he 3rdPt y bi t is s et, in w hich cas e this fiel d spe cifies
the SCSI ID of the initiator to be granted the reservation of the logical unit. The drive
preserves t he reservat ion unti l one of t he fol lowing occurs:
• It is superseded by anothe r valid RESERVE command fr om the ini tiato r.
• It is released by the same initiator.
• It is releas ed by a TARGET RESET messa ge from any initiat or.
• It is released by a hard reset condi tion.
The drive ignores any attempt to release the reservation made by any other initiator.
For exampl e, if ID7 sends ID2 a Third Party r eservation on behalf of ID6 (t he target
at I D2 get s reser ved for the init iator ID6), then only I D7 ca n releas e the t arge t at I D2
(using a Third Party release). ID6 cannot release the reservation even though the res-
ervation was made on it s behalf.
Extent
If 0, request s that t he entire logical unit be reserved for use only by the init iator 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 ext ent reser vation option is implemen ted. This option allows an ap-
plication client in a mult itask ing enviro nme nt to have multiple reser vations .
The size of the extent list is defined by the contents of the Parameter Li st Length
fie ld. T he exten t list consi sts of zero or mor e descript ors. Each descript or defines an
extent beginning at th e specified logi cal bl ock address fo r the specif ied number of
blocks. If the num ber of blocks is 0, the extent begins at t he specified logical bloc k
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.