|
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
RE: iscsi: unsolicited data question
Thanks
to yours and others' explanation, now I am more clear, but I
have
another question:
Based
on your reply, and let me emphasize it by repeating the 4th paragraph
on
page 42 of draft 12-98:
"... If any non-immediate unsolicited data are sent, the total
unsolicited
data MUST be either the negotiated
amount or all the data if the total
amount is less than the negotiated
amount for unsolicited data. ..."
With
this rule, do we still need the F bit in the Data-out (both for the
solicited
and
unsolicited Data-out)? The F bit seems redundant since
the target has
enough
information to figure out the final unsolicited Data-out
and the final
solicited Data-out (based on the FirstBurstSize,
Offset and DataSegmentLength
in
the Data-out, and the
ExpectedDataTransferLength in the
corresponding
SCSI Write PDU).
Thanks,
Dennis
You are wrong
about waiting - read my previous text. You need unsolicited as the amount in one PDU may not be all you
want.
Julo
| Dennis Young
<dyoung@rhapsodynetworks.com> Sent by: owner-ips@ece.cmu.edu
06/12/2002 08:49 PM Please respond to Dennis Young
| To:
Julian Satran/Haifa/IBM@IBMIL cc:
ips@ece.cmu.edu, owner-ips@ece.cmu.edu Subject:
RE: iscsi: unsolicited data question
|
Are you saying that, for a session that has InitialR2T=No in effect,
the initiator must send all its
data as unsolicited first, up to the amount negotiated in FirstBurstSize, before it waits for a R2T from
the target?
Can you shed some light on why we need
unsolicited Data-out PDU when there is ImmediateData, seems like they both serve the same purpose, having
both of them only make the spec
more complex.
Thanks, -Dennis -----Original Message----- From: Julian Satran
[mailto:Julian_Satran@il.ibm.com] Sent: Wednesday, June 12, 2002
10:19 AM To: Dennis Young Cc: ips@ece.cmu.edu;
owner-ips@ece.cmu.edu Subject: RE: iscsi: unsolicited data
question
This is the reason why
the initiator is required to send ALL unsolicited data (target can count on it
and start sending R2Ts as soon as it sees the first header> Neither
bandwidth nor latency are wasted.
Julo
| Dennis Young
<dyoung@rhapsodynetworks.com>
06/12/2002 08:05 PM Please respond to Dennis Young
|
To:
Julian Satran/Haifa/IBM@IBMIL cc:
ips@ece.cmu.edu, owner-ips@ece.cmu.edu Subject:
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
-----Original
Message----- From: Julian Satran
[mailto:Julian_Satran@il.ibm.com] Sent: Wednesday, June 12, 2002
6:05 AM To: Dennis Young Cc: ips@ece.cmu.edu;
owner-ips@ece.cmu.edu Subject: Re: iscsi: unsolicited data
question
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 "
Home
Last updated: Thu Jun 13 10:18:45 2002
10751 messages in chronological order
|