RE: Portal group discovery

[Julian Satran <Julian_Satran@xxxxxxxxxx>]

Dan,

The portal groups have to share more
than a target name - they'll have to have some common state (the CmdSN
etc.).
If behind the routers there is only
the "real" FC target I don't see how you can build a portal out
of several routers. If the target function is in the "real target"
it might as well know who all its front-ends are.

Julo

"Dan Bar Dov" <danb@xxxxxxxxxxxx>

03/10/06 12:00

To	<ips@xxxxxxxx>
cc	"John Hufferd" <jhufferd@xxxxxxxxxxx>, Julian Satran/Haifa/IBM@IBMIL, "William Studenmund" <wrstuden@xxxxxxxxxxxxxxxxx>
Subject	RE: Portal group discovery

Let me try to explain how it can
and does happen.
 
Our iSCSI target device is a "gateway"
(or router). It provides FC SAN 
targets to iSCSI SAN. The iSCSI
target name is generated from the FC WWNN.
 
When there are more then one such
routers in the iSCSI SAN, it is possible and normal
for two (or more) iSCSI routers
to expose the same FC target. This is not by mistake,
rather, it allows fail-over between
such routers, where the initiator uses the multiple portals
for failover.
 
Given such a configuration, how
does the initiator discover it?
option 1: the routers have "cluster
awareness", one router can combine information from the whole
router cluster for sendTargets
response.
option 2: the initiator is configured
with multiple discovery addresses - one per router.
 
If option 2 is used, then the
initiator needs to combine information discovered in discrete sendTargets
responses and produce portal groups.
 
My question relates specifically
to that situation - it is not clear from the iSCSI spec, if such failover

between portals (with the same
pgt) discovered in discrete sendTargets responses is allowed.
 
Thanks,
Dan

---

From: Julian Satran [mailto:Julian_Satran@xxxxxxxxxx]
Sent: Friday, September 29, 2006 8:05 AM
To: William Studenmund
Cc: Dan Bar Dov; ips@xxxxxxxx
Subject: Re:  Portal group discovery


This is not supposed to happen (getting partial data in a session)
If it happens it can be the result of a reconfiguration (between the two
discovery sessions). 

Julo

William Studenmund <wrstuden@xxxxxxxxxxxxxxxxx>

29/09/06 05:31

To	Dan Bar Dov <danb@xxxxxxxxxxxx>
cc	ips@xxxxxxxx
Subject	Re: Portal group discovery

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On Sep 28, 2006, at 7:59 AM, Dan Bar Dov wrote:

> Is it allowed for an initiator to create a single portal group from
 
> information
> collected from two (or more) sendTargets discovery sessions?

I don't think you need two or more SendTargets discovery sessions.  
You are supposed to hear about all portals in one SendTargets  
response, so it's supposed to all be there.

If you had very separate off-load cards, I could see that not being  
followed. But then chances are you can't have a session span said  
cards anyway. :-)

Take care,

Bill
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