RE: Portal group discovery
I guess my confusion with portal group is fully
understanding the way it is
supposed to be used.
When a portal group is used for multiple connections in
the cmnSN must be monotonic and shared among all the ports-
so this indeed is a shared state, and it cannot work with
However, if all I want to achieve is multipath fail-over, I
can have multiple sessions,
or MCS - but with only one session active. In both cases,
the initiator can use an
alternative session or connection, and the cmdSN will
advance just fine.
From all the answers, I understand now that
portals are indeed for MCS, and failover
using multiple devices such as routers, needs to use
multiple sessions (active+standby),
and that distinct devices, even providing the
same service - access to same "real target",
should not, and must not be part of the
same portal group.
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
|"Dan Bar Dov"
<jhufferd@xxxxxxxxxxx>, Julian Satran/Haifa/IBM@IBMIL,
"William Studenmund" <wrstuden@xxxxxxxxxxxxxxxxx>
|RE: Portal group
Let me try to explain how it can and does happen.
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
Given such a configuration, how does the
initiator discover it?
the routers have "cluster awareness", one router can combine information from
router cluster for
the initiator is configured with multiple discovery addresses - one per
If option 2 is used, then the initiator needs to combine information
discovered in discrete sendTargets
responses and produce portal groups.
relates specifically to that situation - it is not clear from the iSCSI spec,
if such failover
(with the same pgt) discovered in discrete sendTargets responses is
From: Julian Satran
Sent: Friday, September 29, 2006
To: William Studenmund
Cc: Dan Bar Dov;
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).
|Dan Bar Dov
|Re: Portal group
-----BEGIN PGP SIGNED
On Sep 28, 2006, at 7:59 AM, Dan Bar Dov
> Is it allowed for an initiator to create a single portal
> 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
If you had very separate off-load cards, I could see that not
followed. But then chances are you can't have a session span
cards anyway. :-)
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