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Title: Message
You mean the "Target
Portal Group B-1", etc labels in those slides? I think John meant to
convey that this is "the target portal group tag 1 within target B" when he
constructed those labels.
Regards,
Marjorie
Hi,
please see below.
The drawing in http://www.haifa.il.ibm.com/satran/ips/EddyQuicksall-iSCSI-in-diagrams/portal_groups.pdf has used the
label "network entity" in a manner inconsistent with the
usage/intent in the iSCSI protocol specification. A "network entity"
is meant to represent a computer system with ethernet egress points.
As a computer system, it can contain one iSCSI Node if it's an initiator,
and one or more iSCSI Nodes if it's a target. It's not
correct to talk about an iSCSI Node "accessing" a network entity, it's a
containment relationship.
[KAG] Yes, this is what confused me. Due to the
accessibility indicated to the storage nodes, according to the iSCSI
draft, I believe all of the Portals shown must belong to the same
"network entity". If the IP-Address values were added to the
Portals, along with the TCP port number, and all Portals, Portal Groups, and
Nodes were associated with one entity - then this figure would make
sense to me..
Portal tags must only be unique within the scope
of a single iSCSI target node, and are 16 bit integers. I don't see
where you get the UTF-8 out of the examples in (1)? I just see
numbers, with no mention of what format they must be exchanged in. Of
course, SendTargets commands are character strings, so the exchange of
TargetPortalGroupTags are integers represented in character format.
[KAG] The
string(i.e.UTF-8) values I mention were used in http://www.haifa.il.ibm.com/satran/ips/iSCSIConfigurationExamples.pdf on the iSCSI Architectural Model (2) and
iSCSI Architectural Model (3) pages. If these were 16 bit integers,
then it would make sense to me. I want to make sure
that only integer values are valid Portal Group Tag definitions.
Yes, the SendTargets command examples in the document did use integer
values for the Portal Group Tags, but the figures did
not.
If there was an entity-relationship model that
defined the iSCSI Architectural model, it would really
help.
Many
Thanks, Kevin
Marjorie Krueger
Networked Storage
Architecture
Networked Storage Solutions
Hewlett-Packard
I have been reviewing the iSCSI Model examples on
http://www.haifa.il.ibm.com/satran/ips , and am trying to get them straight in my head. I was
hoping someone can help.
Network Entity: Can different entities provide access to
the same iSCSI Node? In 1) "iSCSI
Configuration Examples", http://www.haifa.il.ibm.com/satran/ips/iSCSIConfigurationExamples.pdf, the iSCSI Network Entity contains iSCSI Nodes and Network
Portals. Each Network Portal
has a TCP/IP network address. This limits access to an iSCSI Node to one
Entity, and seems to agree with the
architecture model in the iSCSI draft. But 2) "Portal
Groups", http://www.haifa.il.ibm.com/satran/ips/EddyQuicksall-iSCSI-in-diagrams/portal_groups.pdf, shows Network Entities that
provide access to, but do not contain, Network Portals and iSCSI
Nodes. These feed into Portal
Groups and then iSCSI Nodes.
This would mean multiple Entities can provide access
to the same iSCSI Node, and the
example (2) shows this. This seems to disagree with (1). I
tried but could not map this into the iSCSI draft architecture
model.
Portal Tags: Are they uniquely defined using 16 bit
integers? In 1) "iSCSI
Configuration Examples" figures, the
Portal Tags are specified using UTF-8 characters. But the included Send Targets examples use integer
values. In 2) "Portal
Groups", integer values are used for defining Portal Tags.
This seems to agree with the
iSCSI draft.
Is there a UML/entity-relationship model for the iSCSI
architecture? This would help me a
lot. I am aware of one for the iSCSI MIB model, but not the
iSCSI Architecture.
Many
Regards, Kevin
Eddy,
Your point is exactly correct!
The key point that was being missed was the words
at the bottom of the figure on page 40 which says "(within Network Entity, not shown)".
When one has more than one target
(node) within a Network Entity, the portal (IP Address:Port) can be part
of any of the enclosed Targets. That is because the path to the
Target is defined by the portal (IP Address:Port) and the Target Name.
This is reasonable since nothing is ambiguous about the
description of the path that is intended.
Having said that, there is also NO requirement
that all portals need be connectable to all targets within the Network
Entity. This is an implementation decision. (Just thought I
would through that in.)
Your
point is also supported by the figure in section 3.4 and also the
following example that describes what is returned by SendTargets for a
Network Entity that has two iSCSI targets:
- iSCSI Draft20 Appendix D : SendTargets
Operation
"The next example has two internal iSCSI targets,
each accessible via
two different ports with different IP
addresses. The following is
the text
response:
TargetName=iqn.1993-11.com.example:diskarray.sn.8675309
TargetAddress=10.1.0.45:3000,1
TargetAddress=10.1.1.45:3000,2
TargetName=iqn.1993-11.com.example:diskarray.sn.1234567
TargetAddress=10.1.0.45:3000,1
TargetAddress=10.1.1.45:3000,2 "
.
.
John L. Hufferd
Senior Technical
Staff Member (STSM)
IBM/System Group, San Jose CA
Main Office:
(408) 256-0403, Tie: 276-0403, eFax: (408) 904-4688
Home Office:
(408) 997-6136, Cell: (408) 499-9702
Internet Address:
hufferd@us.ibm.com
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| Eddy Quicksall
<eddy_quicksall@ivivity.com>
Sent by: owner-ips@ece.cmu.edu
04/01/2003 05:13 PM
|
To: Kevin Gibbons
<kgibbons@NishanSystems.com>, ips@ece.cmu.edu
cc:
Subject:
RE: iSCSI: Portal Group clarification
|
Yes.
Note however that a Network Portal can belong to more
than one Target Portal
Group but only one Target Portal Group within
a single node (which is a
target in this
context).
Eddy
-----Original Message-----
From: Kevin
Gibbons [mailto:kgibbons@NishanSystems.com]
Sent: Tuesday, April 01,
2003 6:39 PM
To: ips@ece.cmu.edu
Subject: iSCSI: Portal Group
clarification
Hi, I would like to make sure I understand the
iSCSI model correctly. Can
anyone confirm that a Portal,
providing access to a target, is part of
exactly one Portal Group at
a time? My reading of the spec indicates this
is true.
That each Portal has a 16 bit Portal Group tag. But I would
like
to make sure.
I believe that in iSCSI draft 20, it states
that a Portal can be part of
exactly one Portal Group. Please
see page 15:
- Portal Groups: iSCSI supports multiple
connections within the same
session; some implementations will
have the ability to combine
connections in a session across
multiple Network Portals. A Portal
Group defines a set of
Network Portals within an iSCSI Network
Entity that
collectively supports the capability of coordinating a
session
with connections spanning these portals. Not all Network
Portals within a Portal Group need participate in every
session
connected through that Portal Group. One or more
Portal Groups may
provide access to an iSCSI Node. Each
Network Portal, as utilized by
a given iSCSI Node, belongs to
exactly one portal group within that
node.
Also, please see page
39 for similar wording. There is also a
figure on page
40:
----------------------------IP
Network---------------------
| |
|
+----|---------------|-----+
+----|---------+
| +---------+ +---------+
| | +---------+ |
| | Network | | Network | | | |
Network | |
| | Portal | |
Portal | | | | Portal |
|
| +--|------+ +---------+ |
| +---------+ |
|
| |
| | |
|
| |
Portal | |
| | Portal |
| |
Group 1 | |
| | Group 2 |
+--------------------------+
+--------------+
|
|
|
+--------|---------------|--------------------|--------------------+
| |
|
|
|
| +----------------------------+
+-----------------------------+ |
| | iSCSI
Session (Target side)| | iSCSI Session (Target side) | |
| |
| |
|
|
| | (TSIH = 56)
| | (TSIH = 48)
| |
|
+----------------------------+
+-----------------------------+ |
|
|
|
iSCSI Target Node
|
| (within
Network Entity, not shown)
|
+------------------------------------------------------------------+
Please
let me know if I am in error.
Thanks very much!
Kevin
-------------------------------------------------
Kevin
Gibbons
Nishan Systems, Inc.
kgibbons@NishanSystems.com
(408)
519-3756
-------------------------------------------------
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Last updated: Thu Apr 03 20:19:19 2003
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