Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!evax!utacfd!merch!cpe!adaptex!adaptx1!neese
From: neese@adaptx1.UUCP
Newsgroups: comp.periphs.scsi
Subject: Re: LUN on SCSI drives
Message-ID: <283400064@adaptx1>
Date: 5 Mar 91 09:08:13 GMT
References: <1595@unixland.uucp>
Lines: 22
Nf-ID: #R:unixland.uucp:1595:adaptx1:283400064:000:1107
Nf-From: adaptx1.UUCP!neese    Mar  4 13:32:00 1991


>/* ---------- "LUN on SCSI drives" ---------- */
>I'm kind of confused about the "LUN" on SCSI drives...  For 
>example, when I look at my drive configuration using scsicntl,
>it shows both a SCSI id and a LUN for each unit.  I don't see
>any documentation referring to LUN anyplace though.  Is that
>something different from SCSI id?  How is it configured?  I don't
>see any reference to it, at least in my CDC Wren manual (I'm still
>waiting for Maxtor to send me the manual for the 8760S.)

The LUN (Logical Unit Number) is a subset of the controller ID.  In SCSI
you can have a total (currently) of 8 target ID's (0-7) on the SCSI bus.
These target ID's are essentially the controllers/adapters on the bus.
Attached to each target ID/controller you can have 8 LUN's (0-7).  The
LUN is set in the actual SCSI command sent to the target/controller.
All in all you could have 56 devices on the SCSI bus (7 targets with
8 LUNS attached to each target = 56 (This assumes one adapter taking up
one of the target ID slots)).

			Roy Neese
			Adaptec Senior SCSI Applications Engineer
			UUCP @  neese@adaptex