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RE: iSCSI: changing MaxPDUDataLength
How
about if we say that an initiator must not change the MaxPDUDataSize unless it
first idles the commands (at least the ones with the R bit) or
if ErrorRecoveryLevel==0?
That
would simplify target code greatly and would meet the design goals; and since it
should be rare to change it, it would be of little impact to idle the commands
for a split second.
Eddy
I said
only that when you change length you can ask for all PDUs after the ack! (no
need to keep a tall - the old offsets are good up to the hole).
Julo
| Eddy Quicksall
<eddy_quicksall@ivivity.com>
06/11/2002 12:32 AM Please respond to Eddy Quicksall
| To:
Julian Satran/Haifa/IBM@IBMIL cc:
ips@ece.cmu.edu, pat_thaler@agilent.com Subject:
RE: iSCSI: changing MaxPDUDataLength
|
Julian,
Another problem here is that the target
has to calculate the offset from the DataSN #. And as BegRun can be any value.
E.g., BegRun=4 and RunLngth=0 means starting DataSN=4, send all the data for
that sequence.
I think it would be a performance hit
and waist of memory to keep a tally of all PDU sizes just for an occasional
SNACK. It's not that it can't be done ... it is more
that it is messy and I think there is a solution that will satisfy the design
requirements but keep the software simpler. Eddy -----Original
Message----- From: Julian Satran
[mailto:Julian_Satran@il.ibm.com] Sent: Saturday, June 08, 2002
10:16 PM To: Eddy Quicksall Cc: ips@ece.cmu.edu;
owner-ips@ece.cmu.edu; pat_thaler@agilent.com Subject: RE: iSCSI:
changing MaxPDUDataLength
That
is not completely accurate.
The only problem is when PDU size
decreases and then SNACK must be for all data. Target
can also keep a mapping of numbers/to offsets (the list should be small and if
it gets long ask for ack (A-bit).
Julo
| Eddy Quicksall
<eddy_quicksall@ivivity.com> Sent by: owner-ips@ece.cmu.edu
06/08/2002 10:54 PM Please respond to Eddy Quicksall
|
To:
pat_thaler@agilent.com cc:
ips@ece.cmu.edu
Subject: RE: iSCSI: changing
MaxPDUDataLength
|
Thanks,
As a
target, I won't be able to let it change until all of the
outstanding commands are finished (running with ErrorRecoveryLevel>=1).
This is because I must use the PDU size to compute the offset from a
SNACK's BegRun/RunLength.
So, I plan to not give the text response
for a MaxPDURecvDataLength in FFP until I get back an ExpStatSN == next
StatSN.
This will cause a delay of unknown time before the PDU size can
actually change ... do you see any problem with
this?
Eddy
-----Original Message----- From:
pat_thaler@agilent.com [mailto:pat_thaler@agilent.com] Sent: Friday, June
07, 2002 1:13 PM To: eddy_quicksall@ivivity.com;
ips@ece.cmu.edu Subject: RE: iSCSI: changing
MaxPDUDataLength
Eddy,
If one uses a message sync and
steering that relys on the transport segments carrying a full PDU, e.g. TCP
ULP Framing Protocol (TUF), then if the path MTU changes one would want to
change the PDU data length to fit the new
path MTU.
Pat
-----Original Message----- From: Eddy
Quicksall [mailto:eddy_quicksall@ivivity.com] Sent: Wednesday, June 05,
2002 12:24 PM To: ips@ece.cmu.edu Subject: iSCSI: changing
MaxPDUDataLength
Does anybody know a case where it is necessary to
support a new PDU data length during full feature
phase?
Eddy mailto: Eddy_Quicksall@iVivity.com
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