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RE: iscsi: unsolicited data question
Julian,
This
leads me to a more interesting question.
A session with InitialR2T=No in effect, i.e. unsolicited
Data-out
allowed, could cause unintended waste of bandwidth, depending
on
how
fast the target sends our R2T in response to the SCSI Write.
If the
target sees the unsolicited Data-out PDU before building the
R2T,
then everything is fine.
If the
target doesn't see the unsolicited Data-out PDU before
building
the
R2T, the R2T would request the same portion of data in the
unsolicited Data-out, thus bandwidth is wasted.
The
question is, how can a target be smart about this?
Should
the target wait a moment for the possible
unsolicited Data-out
after
receiving each SCSI Write, this sounds kludgy.
Also,
why do we need the unsolicited Data-out PDU feature when
there
is ImmediateData?
Regards,
Dennis
yes -
julo
| Dennis Young
<dyoung@rhapsodynetworks.com> Sent by: owner-ips@ece.cmu.edu
06/12/2002 06:20 AM Please respond to Dennis Young
| To:
ips@ece.cmu.edu cc:
Subject: iscsi: unsolicited data
question
|
I
have a question which has been asked before, but I couldn't find a direct
answer in the archive. The table on page 200 of draft 12 doesn't
directly
answer this question either.
The first paragraph on page 36
of draft 12 says "Targets operate in either
solicitied (R2T) data mode or
unsolicited (non R2T) data mode."
tells me that a target, at all times
during a data sequence transfer, can be
one or the other, but not both
(non R2T for the initial data out, R2T for
the
remaining data). Is
this correct?
Thanks,
Dennis
---snip from an old email dated
3/30/2001---
" Hi Julian
Sorry if I'm covering old ground... Is it
possible to use unsolicited data
for the first burst and then request any
remaining data using R2T? For
example, if the target has a previously
allocated buffer available (length
defined by FirstBurstSize) for
unsolicited data, then once the initiator has
sent unsolicited data up to
and including this amount then the remaining
data (if any) can be requested
using R2T once the target has the buffer
space available.
...Matthew
Burbridge Hewlett Packard, Bristol Telnet: 312 7010
E-mail:
matthewb@bri.hp.com
"