01-173r0 SRP bidirectional residuals

[Elliott, Robert]

* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert" <Robert.Elliott at compaq.com>
*
I promised to review the bidirectional residual text in FCP-2 and have
written a proposal for how SRP should handle this in 01-173r0 (just
submitted for posting).  My recommendation is a bit different than FCP-2 or
iSCSI, since SRP has better support for bidirectional transfers.  I
recommend fixed DATA OUT and DATA IN residuals rather than an OUT or IN
residual (used as OUT for bi-di commands) along with a bi-di IN residual. 

I also added some text to clarify which field the target uses to calculate
residuals: the TOTAL LENGTH field rather than the sum of the scatter gather
list lengths.  This clarification was requested in the March WG.

Finally, I suggested changing the text about keeping some of the redundant
information in sync (e.g. TOTAL LENGTH vs the sum of SG lengths).  The new
wording is simply "The <field> shall be <whatever>" instead of "The <field>
is expected to be <whatever>.  The consequences of <problem> are vendor
specific."

---
Rob Elliott, Compaq Server Storage
Robert.Elliott at compaq.com




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