SCSI-3 Target definition

Ericson, George gericson at clariion.com
Thu Dec 16 11:54:56 PST 1999


* From the T10 Reflector (t10 at t10.org), posted by:
* "Ericson, George" <gericson at clariion.com>
*
Folks,

The SCSI Upper Level Protocol does not define a means to directly address a
SCSI target.  Therefore, all SCSI ULP commands to a target currently must be
directed to some LU of that target.  

SCSI Lower Level Protocols tend to address the SCSI Physical Port.  Since
the relationship between the Physical SCSI Port and the "Logical" SCSI
Target is not restricted by the architecture, this is also not a reliable
means to address a SCSI target.

The LU may show up as unconnected to a physical device,
(Inquiry.PeripheralQualifier == 001b). However, the LU in this case still
exists.

George

-----Original Message-----
From: Gene_Milligan at notes.seagate.com
[mailto:Gene_Milligan at notes.seagate.com]
Sent: Wednesday, December 15, 1999 3:43 PM
To: Lewis, Dan
Cc: t10 at t10.org
Subject: RE: SCSI-3 Target definition


* From the T10 Reflector (t10 at t10.org), posted by:
* Gene_Milligan at notes.seagate.com
*
I copy the reflector in case error as is human:

<<I think I know what you mean.  If a target has multiple logical units, a
REPORT LUNS command could be directed to LUN 0 to discover the other LUNs?>>

     Yes.

<<If the target only has one logical unit, it has to be LUN 0?>>

     Yes.

<<New question:  Does SCSI-3 support the notion of a target with no logical
units?>>

     Maybe. Somewhere there is the capability to report LUN types supported
but
not present. I don't think you can actually get that valid response without
addressing a LUN. I suspect that you determine it by various bad responses
from
the logical unitless target. Earlier versions of SCSI (e.g. SCSI-2) had more
target orientation/functionality and may have some hooks for this. Warning
this
answer is suspected of being error prone since it is from an employee of a
company that has no instances of logical unitless targets. Perhaps Ralph
will
apply error correction.

Gene


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