Re: A question on Zero Copy

[meth@il.ibm.com]

Randall,
We want (B). That's why in the original iSCSI proposal (Feb 2000) we
advocated using RDMA.

- Kalman Meth

"Randall R. Stewart" <randall@stewart.chicago.il.us> on 05/12/2000 19:12:42

Please respond to "Randall R. Stewart" <randall@stewart.chicago.il.us>

To:   iSCSI <ips@ece.cmu.edu>
cc:
Subject:  A question on Zero Copy




Hello all:

Has I am trying to get a grasp of this issue, maybe
someone can fill me in on a conflict I have in
my resolution processing :)


Does the iSCSI layer want:

A) Plain Zero copy, where the upper layer (iSCSI) asks
   to read the next available "message" from the wire
   into a buffer passed to the transport by iSCSI?

<OR>

B) A directed Zero Copy, where the upper layer (iSCSI) asks
   to read a particular request to a specific buffer?


(A) being what I thought as normal zero copy semantics whereas (B)
is something quite different... it implies I can issue several
read requests passing buffers to the underlying transport and
wanting specific things to go in each buffer...


For some reason I may have incorrectly gotten the impression
that iSCSI wants (B), which as I think about it is a
hard problem, or am I just confused and iSCSI wants to use (A)????


Thanks

R
--
Randall R. Stewart
randall@stewart.chicago.il.us or rrs@cisco.com
815-342-5222 (cell) 815-477-2127 (work)