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David Peterson dpeterso at
Mon May 7 11:31:23 PDT 2007

Formatted message: <A HREF="r0705076_f.htm">HTML-formatted message</A>

Below is a resend of a message previously sent to the reflectors. I have
revised the original message upon further review.
There has been no feedback to the previous message and this will be my
final reflector message regarding this issue. 
Note that I have not found any explicit text indicating an Initator may
or shall restart from Relative Offset zero on FCP_DATA IU recovery for a
write operation.
Please respond asap if you have an interest in SRR behavior.
ACTION: HBA vendors to determine whether they need to be able to do
Sequence retry from relative offset 0. 
In the event of Sequence retry, is the initiator allowed to restart from
Relative Offset=0 (implicitly for a write operation, see explicity for a
read operation, see, which forces the target to hold the
application client buffer until confirmed completion (may be megabytes)?
Tape vendors say this is ok for reads, but a problem for writes. They
are able to back up only to the last XFER_RDY point. This seems to work
with all HBAs in use. It is requested to remove the allowance to go back
to zero. 
8.2 Sequence Retransmission Request (SRR)
If the target FCP_Port is unable to retransmit the Sequence or data at
the requested Relative Offset, the target FCP_Port shall respond with an
FCP_RJT Sequence with a reason code of "Unable to perform the command
request" and a reason code explanation of "Unable to supply requested
A target FCP_Port that has agreed during Process Login to support
retransmission should not reject requests for retransmission of the
requested frames unless unusual conditions make the retransmission
impossible. FCP_DATA IU recovery - write operations
After first transmitting the ACC for the SRR, the target FCP_Port
transmits an FCP_XFER_RDY IU in a new Sequence with the Relative Offset
parameter specified by the SRR. FCP_DATA IU recovery - read operations 
The initiator FCP_Port shall set the RELATIVE OFFSET field in the SRR to
that of the next data requested. If the initiator FCP_Port is unable to
determine the Relative Offset of the next data requested, the initiator
FCP_Port shall set the RELATIVE OFFSET field to zero. 
David Peterson
Brocade, Office of the CTO
INCITS T11 International Representative
david.peterson at
cell: 612-802-3299
(no disclaimer)

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