SCSI Surrogate Mode?

Monia, Charles cmonia at corp.adaptec.com
Wed Oct 13 16:10:44 PDT 1999


* From the T10 Reflector (t10 at t10.org), posted by:
* "Monia, Charles" <cmonia at corp.adaptec.com>
*
Hi Paul:

To an initiator, a LUN is part of the target device.  The way that a target
communicates with its LUNs is outside the scope of the standard.
Consequently, as long as the changer appears to the initiator as an SCSI LUN
that supports media changer commands, I don't believe this kind of
implementation needs to be sanctioned by T10.

Charles

-----Original Message-----
From: Paul_A_Suhler at notes.seagate.com
[mailto:Paul_A_Suhler at notes.seagate.com]
Sent: Wednesday, October 13, 1999 3:18 PM
To: t10 at t10.org
Subject: SCSI Surrogate Mode?


* From the T10 Reflector (t10 at t10.org), posted by:
* Paul_A_Suhler at notes.seagate.com
*
Hi, everyone.

It has been suggested to me that a "SCSI Surrogate Mode" is defined by a
SCSI-3 spec.  In this mode of operation, a removable-media drive (e.g.,
tape) has a serial connection to the media changer in which the drive is
installed.  The changer has no SCSI (or Fibre Channel) interface itself.
An initiator sends a media changer command to the drive, but at LUN 1, and
the drive passes it over the serial connection to the changer.  When the
command is finished, the changer sends status to the drive, which sends it
to the initiator.  To the initiator, the target looks like a drive with an
independent media changer, i.e., a loader.

The point of this would be to allow a low-cost changer by saving on a
SCSI/FC interface.

The latest SAM-2 and SPC-2 seem to contain no instances of "surrogate," so
I'm not inclined to believe that it is defined there.

Does anyone know whether this concept has been considered for
standardization?

Thanks,

Paul


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