Subject: RE: [Ips] iSCSI Names and Addresses

From: [email-masked]
Date: Mon, 24 Oct 2005 15:54:07 -0400

Steve,
 
DNS names are associated with hosts, and a host may have
multiple IP addresses.  While an iSCSI name is not the
same as a Ensnare, the same principle applies.  What
may be more interesting is that if a host has multiple
OS images (e.g., courtesy of hardware partitioning or
virtualization), each OS image should have its own
iSCSI name.
 
Thanks,
--David
---------------------------------------------------- 
David L. Black, Senior Technologist 
EMC Corporation, 176 South St., Hopkinton, MA  01748 
+1 (508) 293-7953             FAX: +1 (508) 293-7786 
[email-masked]        Mobile: +1 (978) 394-7754 
---------------------------------------------------- 

  _____  

From: [email-masked] [mailto:[email-masked]] On Behalf Of
Yackey, Steve
Sent: Monday, October 24, 2005 2:25 PM
To: [email-masked]
Subject: [Ips] iSCSI Names and Addresses

I have a novice question. 

When rfc3721 says that iscsi names are associated with iscsi nodes (relevant
portion at the end), what does that mean exactly for a host with multiple
network adapter cards ?

For example, a Win2K03 host might have an initiator named 

- iqn.1991-05.com.microsoft:hosta 

- if there are two network adapters, say, 172.20.4.67 and 172.21.4.67 

How would/should the two paths be represented and/or utilized by the
'outside' world ? 
I do not see how the single initiator name is sufficient for what is
described in 3721. 

Thanks in advance, 
Steve 

[portion of 3721 follows] 

RFC 3721 iSCSI Naming and Discovery April 2004 

1. iSCSI Names and Addresses 

The main addressable, discoverable entity in iSCSI is an iSCSI Node. 
An iSCSI node can be either an initiator, a target, or both. The 
rules for constructing an iSCSI name are specified in [RFC3720]. 
This document provides examples of name construction that might be 
used by a naming authority. 

Both targets and initiators require names for the purpose of 
identification, so that iSCSI storage resources can be managed 
regardless of location (address). An iSCSI name is the unique 
identifier for an iSCSI node, and is also the SCSI device name [SAM2] 
of an iSCSI device. The iSCSI name is the principal object used in 
authentication of targets to initiators and initiators to targets. 
This name is also used to identify and manage iSCSI storage 
resources. 

Furthermore, iSCSI names are associated with iSCSI nodes instead of 
with network adapter cards to ensure the free movement of network 
HBAs between hosts without loss of SCSI state information 
(reservations, mode page settings etc) and authorization 
configuration. 

An iSCSI node also has one or more addresses. An iSCSI address 
specifies a single path to an iSCSI node and consists of the iSCSI 
name, plus a transport (TCP) address which uses the following format: 
<domain-name>[:<port>] 
Where <domain-name> is one of: 
- IPv4 address, in dotted decimal notation. Assumed if the name 
contains exactly four numbers, separated by dots (.), where each 
number is in the range 0..255. 
- IPv6 address, in colon-separated hexadecimal notation, as 
specified in [RFC3513] and enclosed in "[" and "]" characters, as 
specified in [RFC2732]. 
- Fully Qualified Domain Name (host name). Assumed if the <domainname> 
is neither an IPv4 nor an IPv6 address. 
For iSCSI targets, the <port> in the address is optional; if 
specified, it is the TCP port on which the target is listening for 
connections. If the <port> is not specified, the default port 3260, 
assigned by IANA, will be assumed. For iSCSI initiators, the <port> 
is omitted. 

Bakke, et al. Informational [Page 3] 

Steve Yackey 
EMC2 Corporation 
1401 Main Street, Suite 350 
Columbia, SC 29201 
803-231-2632 

Steve Yackey 
EMC2 Corporation 
1401 Main Street, Suite 350 
Columbia, SC 29201 
803-231-2632 

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From: [email-masked]
Date: Mon, 24 Oct 2005 15:58:08 -0400

Steve,
 
Trying again, as the <expletive deleted> spelling corrector
mangled the first attempt:
 
DNS names are associated with hosts, each of which may have
multiple IP addresses.  While iSCSI names are not the same
as DNS names, the same principle applies.  In the reverse
direction, if there are multiple OS images on a host (e.g.,
courtesy of hardware partitioning or virtualization), each
one that uses iSCSI should have its own iSCSI name.
 
Thanks,
--David

  _____  

Thanks in advance, 
Steve 

Steve Yackey 
EMC2 Corporation 

Steve Yackey 
EMC2 Corporation