Subject: Re: iSCSI: INQUIRY page 0x83 identifier

From: "Jim Hafner" <[email-masked]>
Date: Wed, 24 Jan 2001 19:33:17 -0800

JP,

The identifier in this page of Inquiry is NOT at the 'target device' or
'iSCSI device' layer.  It is an identifier for the logical unit to which
the inquiry command was sent.  The FC format was meant primarily for FC
disk drives that have only one logical unit (though it can be used in some
ways by FC controllers, etc.).

The Device (as in a container of one or more logical units) identifier is
yet to be fully defined in SCSI, which is one reason that iSCSI NDT chose
to define such a name for the iSCSI device.

As for an iSCSI type or format for logical unit identifiers:
1) SCSI already allows for an ascii formatted identifier (typically this
includes vendor, model, serial number). Since NDT has defined WWUIs for
DEVICES and these have a defined UTF-8 format, there is nothing to
*prevent* a vendor from using these strings as the starting point for LU
page 83 identifiers of the logical units within that device.
2) But..., iSCSI and NDT should not attempt to make a rule under which
these are used.  FC's intervention in this was more as a strong suggestion,
and is certainly not a requirement.

Did I confuse things even more?

Jim Hafner

Raghavendra Rao <[email-masked]>@ece.cmu.edu on 01/23/2001 08:02:05
AM

Please respond to Raghavendra Rao <[email-masked]>

Sent by:  [email-masked]

To:   [email-masked]
cc:
Subject:  iSCSI: INQUIRY page 0x83 identifier

This may seem like a T10 issue at a high level, but I'm concerned that
SPC-2 (SCSI primary command set) defines in the INQUIRY page 0x83
identifier
type field, a FC identifier type (value = 3).

What identifer type should an iSCSI target use to report a LU identifier
when queried for page 0x83 ? Luckily there seem to be a generic IEEE
extended identifier type (value = 2).

Is the naming and discovery document going to provide a clear defintion
about LU names ? I understand that there should be NO interconnect specific
identifier at the SCSI layer - But SPC-2 is already polluted with a FC
identifier type.

-JP

---

From: "Charles Binford" <[email-masked]>
Date: Thu, 25 Jan 2001 08:45:31 -0600

Jim,  You didn't confuse me more - you made a very good point.  The
identifier is for the LU and is *independent* of the transport.  In fact, it
is vital that the same identifier be given over any path, any transport.
Consider a storage device that has multiple host interfaces, some may be FC,
some may be iSCSI, some may be parallel SCSI.  If a host does an INQUIRY
page x83 to the same LU through any of the above mentioned interfaces, it
better get the same identifier back.

Using an "FC type identifier" does not imply the interface is FC.  It just
specifies the format of the data.  For the binary identifiers, even the
format of the identifier is a 'don't care' to the host as it should treat
them as opaque fields that can be matched, but not parsed.  By following the
format rules, however, the LU can ensure the identifier it gives is
world-wide unique.

Charles Binford
Blue Spruce Networks
office/cell: (316) 210-6404
e-fax: (509) 756-4425

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of
Jim Hafner
Sent: Wednesday, January 24, 2001 9:33 PM
To: [email-masked]
Subject: Re: iSCSI: INQUIRY page 0x83 identifier

JP,

[deleted]

Jim Hafner