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FCP Information Units
48
T10000: Interface Reference Manual • January 2011
• E20425-01
Command Information Unit
The Command Information Unit (T1) is a single-frame sequence.
For all commands that transfer data to the tape drive:
FCP_DL (data length) in the FCP_CMND payload always equals the number
of bytes being transferred for the command.
For SCSI commands which specify the transfer length in blocks in the
Command Data Block (CDB), the FCP_DL equals the Transfer_Length x the
Block_Size.
Note:
If the FCP_DL value is less than the transfer length then FCP_DL data
will be transferred and the command will be terminated with Check
Condition. The Sense Key will be 0x5, the ASC will be 0x4B, and the
ASCQ will be 0x80.
For all commands that transfer data from the tape drive:
The SCSI Initiator is responsible for making sure the amount of data returned
is equal to the amount specified by FCP_DL. Even if Good Status is returned.
If the amount does not match FCP_DL, a command-specific ULP recovery
action needs to be invoked. Because there are no transfers of Sequence
Initiative during read operations, once the SCSI Target receives the T1
Information Unit, it may return Good status even though some of the data was
not received by the SCSI Initiator. This can occur as the result of lost or
corrupted frames in the read data.
Note:
The way a SCSI Initiator determines the correct amount of data is
returned depends on the implementation and includes counting the
number of bytes returned, computing the number of bytes received by
use of the relative offsets.
The FCP Command Reference Number (CRN) shall be used to ensure proper
ordering of Exchange’s (SCSI commands). CRN usage is enabled based on
I_T_L nexus by setting the Enable Command Reference Number (ECRN) bit
to one in the FC Mode Page (0x19) for the LUN. Task Management functions
shall set the CRN value to zero.
Note:
The drive currently does not support command queuing, thus CRN’s
are not supported.
Table 27. FCP 8-Byte LUN
Byte 0
Byte 1
Byte 2
Byte 3
Byte 4
Byte 5
Byte 6
Byte 7
00
LUN
00
00
00
00
00
00
Содержание Storage Tek T10000
Страница 14: ...Tables xiv T10000 Interface Reference Manual January 2011 E20425 01...
Страница 18: ...What s New xx T10000 Interface Reference Manual January 2011 E20425 01...
Страница 30: ...Considerations 12 T10000 Interface Reference Manual January 2011 E20425 01 Figure 5 Cascading Hubs...
Страница 82: ...Private Loop SCSI Target Discovery 64 T10000 Interface Reference Manual January 2011 E20425 01...
Страница 286: ...Glossary 268 T10000 Interface Reference Manual January 2011 E20425 01...