Report LUNs if more than 256 LUNs on the same bus

Gerry.Houlder at seagate.com Gerry.Houlder at seagate.com
Tue Apr 1 07:32:08 PDT 2008


* From the T10 Reflector (t10 at t10.org), posted by:
* Gerry.Houlder at seagate.com
*
There are some options on this. Please refer to SAM-4, clause 4.7 for a
full description on this. My opinions listed here:
(a) You could use peripheral device addressing method, where 2 most
significant bits of byte 0 are set to 00 binary. This groups the LUNs on
different buses (6 bits of byte 0 consists of a bus identifier) with up to
256 LUNs per bus. The effective address space for this is
00 00 00 00 00 00 00 00 through 3F FF 00 00 00 00 00 00.
(b) You could use the flat space addressing method, where the 2 MS bits of
byte 0 are set to 01 binary.
This gives LUNs 40 00 00 00 00 00 00 00 through 7F FF 00 00 00 00 00 00.
 If this isn't enough for you, you need to use the multilevel structure
defined later in the clause. If you need that much space, you definitely
need to read SAM-4.
	     "Marian Lakov"						   
	     <Marian_Lakov at us.						   
	     xyratex.com>						To 
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				       Report LUNs if more than 256 LUNs   
				       on the same bus			   
	     03/31/2008 03:38						   
	     PM 							   
Hi,
If a RAID controller presents more than 256 LUNs to a host on the same bus
what is the proper LUN format?
00 00 00 00 00 00 00 00 to 00 00 00 00 00 00 00 FF for the LUNs 0 to 255
and
40 00 00 00 00 00 01 00 to 40 00 00 00 00 00 3F FF for the LUNs above 255
or
40 00 00 00 00 00 00 00 to 40 00 00 00 00 00 3F FF for all the LUNs
Also, for the LUNs above 255, is it possible to use 00 00 00 00 00 00 01 00
to 00 00 00 00 00 003F FF format?
Thanks,
Marian
________________________
Marian Lakov
Systems Engineer
Xyratex
1804 Centre Point Circle, Suite #112
Naperville, IL 60563
Office:  630-364-7600
Fax:	 630-364-7601
marian_lakov at us.xyratex.com
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