User Manual

SCSI Commands Reference Manual, Rev. J 277
www.seagate.com Direct Access Block commands (SPC-5 and SBC-4)
ANCHOR and UNMAP bits
If the logical unit supports logical block provisioning management (see SBC-4), then the ANCHOR bit, the UNMAP bit, and the ANC_SUP bit in
the Logical Block Provisioning VPD page
(see 5.4.13) determine how the device server processes the command as described in Table 237.
NUMBER OF BLOCKS field
The NUMBER OF BLOCKS field specifies the number of contiguous logical blocks to be written, starting with the logical block specified by the
LOGICAL BLOCK ADDRESS field. A NUMBER OF BLOCKS field set to zero specifies that the device server write all the logical blocks starting with
the one specified in the LOGICAL BLOCK ADDRESS field to the last logical block on the medium. If the logical block address plus the number of
blocks exceeds the capacity of the medium, the device server shall terminate the command with CHECK CONDITION status with the sense key
set to ILLEGAL REQUEST and the additional sense code set to LOGICAL BLOCK ADDRESS OUT OF RANGE.
Table 237 ANCHOR bit, UNMAP bit, and ANC_SUP bit relationships
UNMAP bit
[a]
ANCHOR bit
ANC_SUP bit
[b]
Action
0b
0b n/a
Write
[c]
1b n/a
Error
[d]
1b
0b n/a
Unmap
[e]
1b
0
Error
[d]
1
Anchor
[f]
[a] The device server in a logical unit that supports logical block provisioning management (see SBC-4) may implement the UNMAP bit.
[b] See the Logical Block Provisioning VPD page (see 5.4.13).
[c] The device server shall perform the specified write operation on each LBA specified by the command.
[d] The device server shall terminate the command with CHECK CONDITION status with the sense key set to ILLEGAL REQUEST and the addi-
tional sense code set to INVALID FIELD IN CDB.
[e] The device server in a thin provisioned logical unit should deallocate each LBA specified by the command (see SBC-4) but may anchor each
LBA specified by the command (see SBC-4). The device server in a resource provisioned logical unit should anchor each LBA specified by
the command. If the device server does not deallocate or anchor the LBA, then the device server shall perform the specified write opera-
tion (see SBC-4).
[f] The device server should anchor each LBA specified by the command (see SBC-4). If the device server does not anchor the LBA, then the
device server shall perform the specified write operation (see SBC-4).