Seagate Fibre Channel Interface - Manual (Page 359)

Fibre Channel Interface Manual, Rev. D 345
12.70 XDWrite (10) command
The XDWrite (10) command requests that the target xor the data transferred with the data on the medium. The
resulting xor data is stored by the target until it is retrieved by an XDRead command.
The resulting xor data is retrieved by an XDRead command with starting logical block address and transfer
length fields that match, or is a subset of, the starting logical block address and transfer length of this com-
mand.
If the logical unit is reserved, a reservation conflict occurs when an XDWrite command is received from an ini-
tiator other than the one holding the logical unit reservation. The command is rejected with Reservation Con-
flict status if the reservation conflict is due to a logical unit reservation. The XDWrite command is evaluated for
extent reservation conflicts. XDWrite commands with a reservation conflict are terminated with Check Condi-
tion status and the sense key is set to Data Protect if any part of the XDWrite operation is prohibited by an
extent reservation.
Field definitions (listed alphabetically)
Control
See Section 11.2.1.6.
Disable Write
0
The data transferred from the initiator is written to the medium after the xor operation is complete.
1 The data is not written to the medium.
DPO (Disable Page Out)
0
The priority is determined by the retention priority fields in the caching page. All other aspects of the algorithm imple-
menting the cache memory replacement strategy are not defined.
1 The device server assigns the logical blocks accessed by this command the lowest priority for being fetched into or
retained by the cache. This value overrides any retention priority specified in the caching page.
FUA (Force Unit Access)
0
The device server may satisfy the command by accessing the cache memory.
For read operations, any or all of the logical blocks that are contained in the cache memory may be transferred to
the application client directly from the cache memory.
Table 235: XDWrite (10) command (50h)
Bit
Byte
7 6 5 4 3 2 1 0
0 0 1 0 1 0 0 0 0
1
Reserved DPO FUA
Disable
Write
Reserved
2
Logical Block Address (MSB)
3
Logical Block Address
4
Logical Block Address
5
Logical Block Address (LSB)
6
Reserved
7
Transfer Length (MSB)
8
Transfer Length (LSB)
9
Control
50h
Table
number
235
235
235
235