LUN numbering in 8 byte LUN field

John Tyndall jtyndall at crossroads.com
Tue Sep 24 13:52:52 PDT 2002


* From the T10 Reflector (t10 at t10.org), posted by:
* "John Tyndall" <jtyndall at Crossroads.com>
*
Now you have me confused. I thought SAM-2 was very explicit about non-hierarchical addressing at least for targets that support 256 or fewer logical units. There is a table for the format in section 4.8. However, it does not say anything about the possibility of a non-hierarchical target supporting more than 256 logical units.

John Tyndall
Architect
Crossroads Systems Inc.
Email  : jtyndall at crossroads.com
Phone : 512-928-7282


-----Original Message-----
From: George Penokie [mailto:gop at us.ibm.com] 
Sent: Tuesday, September 24, 2002 2:43 PM
To: Gerry.Houlder at seagate.com
Cc: owner-t10 at t10.org; t10 at t10.org
Subject: Re: LUN numbering in 8 byte LUN field


* From the T10 Reflector (t10 at t10.org), posted by:
* George Penokie <gop at us.ibm.com>
*




Gerry,

This is a confusing point but basically SAM-2/3 only defines the LUN format is the HISUP bit is set to one. There is no format defined for the LUN if the HISUP bit is set to zero so it could be anything. The only thing that saves us is that for single LU devices is that the LUN is zero which is the same regardless of the HISUP bit setting. The moral here is that if you have a LUN other than zero then you better support the REPORT LUNs command so you can set the HISUP to one and then use the hierarchical format defined in SAM-2/3.


Bye for now,
George Penokie

Dept 2C6  114-2 N212
E-Mail:    gop at us.ibm.com
Internal:  553-5208
External: 507-253-5208   FAX: 507-253-2880




                                                                                                                                       
                      Gerry.Houlder at sea                                                                                                
                      gate.com                 To:       t10 at t10.org                                                                   
                      Sent by:                 cc:                                                                                     
                      owner-t10 at t10.org        Subject:  LUN numbering in 8 byte LUN field                                             
                                                                                                                                       
                                                                                                                                       
                      09/24/02 01:11 PM                                                                                                
                                                                                                                                       
                                                                                                                                       



* From the T10 Reflector (t10 at t10.org), posted by:
* Gerry.Houlder at seagate.com
*
I have a question about the interpretation of LUN number in an 8 byte LUN field (e.g., SPI_LQ packet in packetized parallel SCSI). With the bytes in the LUN field numbered 0 through 7 (0 being in byte 4 of LQ packet, 1 in byte 5 of LQ packed, etc.), how is LUN 4 expressed?

Per the model in SAM-2, if the target sets the HiSup bit in standard Inquiry data, it should be:

00 04 00 00 00 00 00 00

If the target doesn't set the HiSup bit, is it this?

00 00 00 00 00 00 00 04

Or is it required to be the same as the first interpretation?

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