RE: Portal group discovery

["Sandars, Ken" <ken_sandars@xxxxxxxxxxx>]

Dan,

 

The RFC is very clear about this. In your option 2 scenario, each router which provides a path to the target MUST advertise an unique Target Portal Group Tag (TPGT). The simplest reason is that you have no way to join connections on different routers into the same iSCSI session.

 

The way you achieve this is implementation-specific.

 

HTH,

Ken

---

From: Dan Bar Dov [mailto:danb@xxxxxxxxxxxx]
Sent: Tuesday, 3 October 2006 20:01
To: ips@xxxxxxxx
Cc: William Studenmund; John Hufferd; Julian Satran
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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