FW: Unit Attention with multiple LUNs?

DeKoning, Rod rdekonin at ppdpost.ks.symbios.com
Thu Nov 21 06:12:00 PST 1996


* From the SCSI Reflector (scsi at symbios.com), posted by:
* "DeKoning, Rod" <rdekonin at ppdpost.ks.symbios.com>
*

Brian,
Your issue is commonly seen in all multi-LUN environments and, in 
particular, many RAID systems.  I would make the following changes to your 
first table to support multi-initiator environments:

    cmd issued       LUN(s)
      to LUN        affected       UA for LUN0?        UA for LUN1?
   ------------   -------------   --------------       --------------
        0               0       Issuing Initiator NO          NO
                    Other Initiators YES

        0             0,1       Issuing Initiator NO          YES
                    Other Initiator YES

        0               1               NO                  YES


        1               0              YES                    NO

        1             0,1              YES             Issuing Initiator NO
                                        Other Initiators YES

        1               1               NO                Issuing Initiator 
NO
                                     Other Initiators YES


Rod DeKoning
Symbios Logic

 ----------
From: scsi-owner
To: scsi
Subject: Unit Attention with multiple LUNs?
Date: Wednesday, November 20, 1996 4:47PM

* From the SCSI Reflector (scsi at symbios.com), posted by:
* Brian_Moyle at asd.sel.sony.com
*
I have been discussing the following question with one of my
colleagues.  We are unsure of the correct SCSI response for the
following scenario.

In an autoloader that can accept move medium commands to either LUN 0
or LUN 1, how should the Unit Attention conditions be handled after a
move medium command?  We feel the following is the appropriate
response, regardless of the command, but we're not sure if it's
consistent with the SCSI-2 specification (section 7.9, "Unit
attention condition"):

    cmd issued       LUN(s)
      to LUN        affected       UA for LUN0?     UA for LUN1?
   ------------   -------------   --------------   --------------
        0               0               NO               NO
        0             0,1               NO              YES
        0               1               NO              YES

        1               0              YES               NO
        1             0,1              YES               NO
        1               1               NO               NO

Is this correct?  In other words, is it okay to assume that an
initiator remembers the last command it sent to a LUN and that it
does not need additional reminding with a Unit Attention?

The SCSI-2 specification, if read conservatively, seems to indicate
something different:

    cmd issued     cmd affects
      to LUN          LUN(s)       UA for LUN0?     UA for LUN1?
   ------------   -------------   --------------   --------------
        0               0              YES              YES
        0             0,1              YES              YES
        0               1              YES              YES

        1               0              YES              YES
        1             0,1              YES              YES
        1               1              YES              YES

Is this second method preferred?

Sincerely,

 -Brian
 -----------------------------------------------------
Brian Moyle
Advanced Storage Development/Sony Electronics Inc.
Mail Drop: SJ-3B2
3300 Zanker Road
San Jose, CA 95134-1940
Phone: 408-955-5698
Fax:   408-955-5066
e-mail: Brian_Moyle at asd.sel.sony.com

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