Subject: RE: iSCSI: login issue - partial consensus call

From: "John Hufferd" <[email-masked]>
Date: Thu, 6 Sep 2001 10:51:52 -0700

Eddy,
I believe you have this wrong.  The iSCSI Initiator Node Name comes from
the OS, NOT the HBA.  The iSCSI Initiator function is suppose to use the
same iSCSI Initiator Node Name as that was assigned to the  OS.  The OS is
suppose to have some method to send to the iSCSI HBA,  the iSCSI Initiator
Node Name so that it can configure itself to use that Name.

If this was not True then the Authentication would be based on the Adapter
interface, as it is in FC, instead of the OS.  We did not want the
administrator to have to know about all those HBAs, only names associated
with OSs.

By the way, the OS is also suppose to have a way to hand out (partition up)
ISIDs to the various iSCSI Initiator functions, whether they are Software
or Hardware.

So, even though,  I was initially swayed by Nick's Arguments -- we require
the OS to partition up the ISID space and hand out specific ISIDs or ranges
of ISIDs (in some manor) to the iSCSI Initiator functions (regardless of
whether they are in Software or Hardware) -- I do not now see, if the
implementation is as specified in our spec., how there is a conflict in
ISID.
.
.
.
John L. Hufferd
Senior Technical Staff Member (STSM)
IBM/SSG San Jose Ca
Main Office (408) 256-0403, Tie: 276-0403,  eFax: (408) 904-4688
Home Office (408) 997-6136
Internet address: [email-masked]

"Eddy Quicksall" <[email-masked]>@ece.cmu.edu on 09/06/2001
07:56:50 AM

Please respond to <[email-masked]>

Sent by:  [email-masked]

To:   <[email-masked]>, <[email-masked]>
cc:
Subject:  RE: iSCSI: login issue - partial consensus call

But wouldn't the two different vendors you mention below have different
iSCSI Initiator Names? Remember, the Initiator is not the host, it is the
HBA in this case.

If two different HBA's are going to play together then a common driver
would
be used and the driver would provide the iSCSI Initiator Name. Then, the
ISID would be properly maintained by the driver.

Think of the Initiator Name as the owner of the ISID's for that name.

Eddy

-----Original Message-----
From: Martin, Nick [mailto:[email-masked]]
Sent: Wednesday, September 05, 2001 5:50 PM
To: KRUEGER,MARJORIE (HP-Roseville,ex1); [email-masked]
Subject: RE: iSCSI: login issue - partial consensus call

Marj,

You mention vendors not knowing how to play right.
The problem is that iSCSI does not and will not specify how two HBAs
from different vendors installed in the same Initiator should or could
get a range of ISIDs for their exclusive use.  This will be operating
system specific and vendor defined.  It is uncertain that the same tool
or repository would be used by all HBA vendors in any environment.
Given this, accidental overlap in ISID space is not unlikely.

Given that there is no one way to play right, we must make sure that
everyone can at least play nice.

My expectation is that sessions are infrequently established and long
lived.  ISIDs may be re-used at will by their current owners.  When no
"already owned" ISIDs are available, or an attempt to re-use an "already
owned" ISID failed, and HBA would need to a) "probe" for a new available
ISID or b) fail the request to establish the session.  Session recovery
should not be attempted unless a session is known to have failed.

If tools are available, and the administrator has used them correctly,
then HBAs will not collide in ISID space.  If the tools are not
available or were not used correctly, I would hope the second HBA can
still attempt to come up without impacting the sessions established by
the first.

Again, I state my support for a login with existing ISID harmlessly
fails (the Target state does not change) unless a session recovery
indicator is set.  Also if a session recovery indicator is set, and the
ISID is not in use (by this Initiator at this Target), the login also
fails.

Thanks,
Nick
-----Original Message-----
From: KRUEGER,MARJORIE (HP-Roseville,ex1)
[mailto:[email-masked]]
Sent: Friday, August 31, 2001 12:09 PM
To: Martin, Nick; [email-masked]
Subject: RE: iSCSI: login issue - partial consensus call

> In particular this enables independent agents within the same
initiator to
> attempt a login without knowing all ISIDs in use by other agents.
Each
> agent would know the ISID of sessions it had successfully
established,
but
> not the ISIDs for sessions established by others.  It can use the
ISIDs it
> knows to recover sessions it owns.  If an agent gets a  failure
attempting
to
> establish a new session, it would pick a different ISID and
> retry (or just quit), rather than disrupting a session of another
agent.

The intent of the presentation on SCSI/iSCSI modeling, and the text in
the
draft, is to illustrate how this example is not a recommended
implementation
choice due to the probability of violating the SCSI/iSCSI rules pointed
out.
If the "independant agents" had partitioned the ISID space, there would
be
no collision on login and no time wasted.  Your illustrated
implementation
could spend significant time "trying" ISID's in use by the "other
agents".

However, I'm starting to have more sympathy with Julian's concerns due
to
the apparent risks of different vendors' initiator implementations not
following the rules.

I just imagined having vendor A's HBA installed and happily servicing
applications, installing vendor B's "plug-n-play" implementation, and
having
all A's sessions aborted cause B doesn't know how to play right :-(

Marj

---

From: Sandeep Joshi <[email-masked]>
Date: Thu, 06 Sep 2001 14:44:00 -0400

John,

Is this what you are referring to ? (Sec 1.3 of Naming & Discovery)

> b) The ISID name space of the iSCSI Initiator should be partitioned  
>       among the intiator portal groups.

How do you perceive this will be achieved in practice ?

This can turn out to be an nightmare for HBA vendors.
IRQ settings, jumpers, or setup programs which run at boot 
instantly come to mind.  

Ideally, ISIDs should work as SCAM works but that would involve 
adding a mid-layer to OSes, to distribute that ISID name space.
Modifying OSes in the field is tough, as we all know.

I realize the standard wont mandate such configuration items
but I'd rather we not add rules which would force such
configuration tweaks to become necessary.  

We should reconsider the above rule and its consequence on
the login issue Nick brought up.

Regards,
-Sandeep