RE: iSCSI question

[Shahram Davari <Shahram_Davari@pmc-sierra.com>]

Pat,

 

Thanks. I understand your point. Although terminating a session may be easy, but, starting a new session requires new login, parameter exchange, new connections establishment, authentication, etc. So I wonder how is this any simpler than a simple PDU retransmit?

 

Yours,

-Shahram

-----Original Message-----
From: pat_thaler@agilent.com [mailto:pat_thaler@agilent.com]
Sent: Thursday, August 08, 2002 2:19 PM
To: Shahram Davari; Julian_Satran@il.ibm.com
Cc: ips@ece.cmu.edu; owner-ips@ece.cmu.edu
Subject: RE: iSCSI question

Shahram,

 

Wen you start a new session, you don't recover any PDUs. All the iSCSI state died with the old session. iSCSI doesn't know the new session had any relationship to the old session.

 

As Julian said, recovery at that point is up to the SCSI layer above iSCSI. It is up to SCSI to retry any commands that it wants to retry. When SCSI retries a command, iSCSI doesn't know it is a retry. To the iSCSI layer it is just like any other SCSI command it receives.

 

Pat

 

-----Original Message-----
From: Shahram Davari [mailto:Shahram_Davari@pmc-sierra.com]
Sent: Wednesday, August 07, 2002 8:44 AM
To: 'Julian Satran'
Cc: ips@ece.cmu.edu; owner-ips@ece.cmu.edu
Subject: RE: iSCSI question

Julian,

 

To start a new session you need to start new connections and you need to support

the PDU recovery. So how is that a subset of PDU and connection recovery?

 

 

-Shahram

 

(I will explain the detailed clarity issues in another email)

-----Original Message-----
From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
Sent: Wednesday, August 07, 2002 11:34 AM
To: Shahram Davari
Cc: ips@ece.cmu.edu; owner-ips@ece.cmu.edu
Subject: RE: iSCSI question

Session recovery is in fact leaving all recovery to SCSI - it drops everything and creates a new session.
As for you comment on the clarity of chapter 5 at this stage it makes sense to be either specific
or keep this type of comment out of this context.

Julo

Shahram Davari <Shahram_Davari@pmc-sierra.com> 08/07/2002 06:09 PM

To:        Julian Satran/Haifa/IBM@IBMIL         cc:        ips@ece.cmu.edu, owner-ips@ece.cmu.edu         Subject:        RE: iSCSI question

Julian,
 
Thanks. I have read that section but it is not very clear.
 
I also agree that Connection recovery requires everything in command recovery.
But what about session recovery? isn't it a superset of both connection and command recovery?
 
Yours,
-Shahram
-----Original Message-----
From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
Sent: Wednesday, August 07, 2002 11:03 AM
To: Shahram Davari
Cc: ips@ece.cmu.edu; owner-ips@ece.cmu.edu
Subject: Re: iSCSI question


Sharam,

You may want to go over the recovery chapter.
It has detailed answers to all your questions.
The superset/subset is based on functions you need for the next level.

Session recovery drops real recovery to SCSI.
Command recovery recovers from individual command errors without
changing connection and the highest enable you to switch to a new connection and
continue commands there.

2 requires everything in 1.

Julo

Shahram Davari <Shahram_Davari@pmc-sierra.com> Sent by: owner-ips@ece.cmu.edu 08/07/2002 05:17 PM

To:        ips@ece.cmu.edu        cc:                Subject:        iSCSI question

Hi,

I have a question regarding the hierarchy of error recovery.
Section 6.13 mentions the hierarchy as:

2: Connection recovery
1: Digest failure recovery
0: Session recovery

And it states that the higher levels are a superset of the
lower levels and that the level of complexity increases from 0->1->2.

Couple of questions:

1) How is digest failure recovery done? by retransmission of PDUs?
2) Why is the connection recovery a superset of session recovery
and more complex?
3) It seems to me the order should be:

2: Session recovery
1: Connection recovery
0: Digest failure recovery


I appreciate any insight.

Thanks,
-Shahram