[T11.3] Re: FCP-3: Obsolete FCP_DL and FCP_BIDIRECTIONAL_DL

Jim.Coomes at seagate.com Jim.Coomes at seagate.com
Fri Oct 1 14:34:27 PDT 2004






This issue of obsoleting FCP_DL and FCP_BIDIRECTIONAL_DL was raised due to
a change in processing these fields in FCP-3.

The function of the FCP_DL field in FCP and FCP-2 required targets to do
truncated transfers, set flags and return residual counts when the CDB
length and the FCP_DL field did not agree. Disk drive and RAID vendors have
implemented the checking and transfer behavior to this requirement. This
has lead to many test conditions for compliance to the required behaviors.

Tape vendors find the truncated transfers unacceptable. Recovery from a
partial transfer could easily require a repositioning of the tape.

In FCP-3, the recommended response ( a "should") to FCP_DL and
FCP_BIDIRECTIONAL_DL field values that do not match the expected transfer
length identified in the CDB is to fail the command with no transfer and
check condition.

As currently documented in FCP-3, disk drive and RAID vendors "should" fail
commands with FCP_DL and FCP_BIDIRECTIONAL_DL field values considered in
error.

Is failing the command acceptable to current implementation?

Jim


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