Name that multi-port SCSI device

Gerry_Houlder at notes.seagate.com Gerry_Houlder at notes.seagate.com
Mon May 24 09:31:22 PDT 1999


* From the T10 Reflector (t10 at symbios.com), posted by:
* Gerry_Houlder at notes.seagate.com
*
This is a response to Bob Snively's statement:


The basic defect with the SCSI "device" concept is that a SCSI device is a
rather arbitrary box that shows SCSI target and/or initiator behavior at
one or more of its multiple ports and presumably has enough concept of
LU to answer INQUIRY and REPORT LUNS.



This statement sounds like a description of "target" or possibly "port"
behavior to me. I see the the definition of "SCSI device" in SAM is a lot
more wispy than my concept of device, but I use the the term "SCSI device"
as a fully functional SCSI entity that encompasses a target/initiator and
logical unit (minimum) and optionally may include multiple LUs or multiple
"ports". This makes more sense in the context of the SPI and command set
documents. It sounds like some other people are reading a much more
limiting definition of "device".

I would rather not see device be used where we specifically mean "target",
"port", "logical unit", or any of the various sub-pieces that we have names
for already. A device should include as many of each sub-piece as needed to
achieve a fully functional 'thingy". Then we can have a "multi-port SCSI
device" or a "multi-LU SCSI device" which simply describes a SCSI device
that has more than the required minimum of of a particular sub-piece. This
is much less confusing that a new name.





Bob Snively <bob.snively at ebay.sun.com> on 05/24/99 10:34:05 AM

Please respond to Bob Snively <bob.snively at ebay.sun.com>

To:   t10 at Symbios.COM
cc:    (bcc: Gerry Houlder)

Subject:  Re: Name that multi-port SCSI device




* From the T10 Reflector (t10 at symbios.com), posted by:
* Bob Snively <bob.snively at ebay.sun.com>
*

------------- Begin Forwarded Message -------------

Date: Thu, 20 May 1999 13:17:32 -0700 (PDT)
From: Bob Snively <snively at ha10nwk>
Subject: Re: Name that multi-port SCSI device
To: roweber at acm.org
Mime-Version: 1.0
Content-MD5: 7aY4Vmp789Ok2gJFlGjRhA==


Ralph,

I was playing with this for a few moments and thought about what we
were really trying to express.

The concept is that a LUN has more than one connectivity nexus available to
it.  That connectivity nexus is an IT nexus.  Task queues are maintained
by logical unit, not by target.  The only target oriented activity is
the occassional mode-select associated with path capabilities.
Proper names might then be:

     SCSI multiple connection logical unit
          This becomes SMCLU pronounced smuckloo.

     Multiple Connection Logical Unit (since LU is already SCSI)
          This becomes MCLU pronounced muckloo.

     Multi-path Logical Unit
          This becomes MPLU pronounced muploo, or MLU pronounced Emloo

The basic defect with the SCSI "device" concept is that a SCSI device is
a rather arbitrary box that shows SCSI target and/or initiator behavior at
one or more of its multiple ports and presumably has enough concept of
LU to answer INQUIRY and REPORT LUNS.

You are free to post this or call me at 510-574-9051.

Bob



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