Re: iSCSI: Check Condition and Residuals

[Santosh Rao <santoshr@cup.hp.com>]

It sounds to me like there is a mis-understanding here on who owns the
"RESID" field. 

FCP-2 makes it clear that it is the FCP-2 SCSI LLP in the target that
should initialize this field based on FCP_DL and its state information
on the bytes transferred. IOW, this is a field owned by the scsi
transport and should be initialized/computed by the scsi transport. (See
FCP-2 Rev 07a Section 9.4.8).

It sounds like folks here are assuming the the SCSI device server is
going to provide this information to the iSCSI LLP layer in the target
and the iscsi target layer would then copy this information into the
Response PDU. 

It is upto the iSCSI layer to initialize the RESID field anytime a data
underflow or overflow condition occurs. Perhaps, the RESID field
definition should provide guidelines on how the iscsi target layer
should compute the RESID, as is done by FCP-2 Section 9.4.8.

- Santosh


Luben Tuikov wrote:

> Be that as it may, BUT you _were__spilling_ it into iSCSI.
> 
> AND iSCSI is clear on that! Residuals are valid only when
> the appropriate bit is set (o/O/u/U).
> 
> Also your mail _is_suggestive_ of peeking into the sense data,
> since you mention that status should be irrelevant for residuals.
> (Again spilling this into iSCSI!)
> 
> This has _always_ been and still is a NON-ISSUE for me.
> 
> Again, iSCSI is clear, and as complete on residuals as anything
> else out there.
> 
> If anyone has a problem with this, they should raise the issue
> with T10 for a poke at SAM and/or SPC (whatever _they_ decide).


-- 
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some blunders and absurdities have crept in; forget them as soon as 
you can. Tomorrow is a new day; you shall begin it serenely and 
with too high a spirit to be encumbered with your old nonsense.