Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!olivea!uunet!zds-ux!gerry
From: gerry@zds-ux.UUCP (Gerry Gleason)
Newsgroups: comp.periphs.scsi
Subject: Re: LUN on SCSI drives
Message-ID: <560@zds-ux.UUCP>
Date: 6 Mar 91 17:23:56 GMT
References: <1991Mar2.184349.1595@unixland.uucp> <1991Mar4.185942.1554@seachg.uucp>
Reply-To: gerry@zds-ux.UUCP (Gerry Gleason)
Organization: Zenith Data Systems
Lines: 20

In article <1991Mar4.185942.1554@seachg.uucp> db@seachg.UUCP (David Bell) writes:
>In article <1991Mar2.184349.1595@unixland.uucp> bill@unixland.uucp (Bill Heiser) writes:
>>I'm kind of confused about the "LUN" on SCSI drives...  For 

>The SCSI spec allows up to 8 controllers on the bus, with SCSI id's from 0
>to 7. Each controller may have up to four devices connected to it, with
>Logical Unit Numbers from 0 to 3.

Only partially correct.  LUN is a 3 bit field, therefore 0-7 are
possible.  Also, there is provision for a sub-LUN, via an extended
message which is 8 more bits.  (Wait let me make sure)

Yes, that's it.  You send:

01h	Extended message
02h	Extended message length
02h	EXTENDED IDENTIFY code
XXh	Sub-logical unit number

Gerry Gleason