SCSI Surrogate Mode?

Paul_A_Suhler at Paul_A_Suhler at
Fri Oct 15 09:14:12 PDT 1999

* From the T10 Reflector (t10 at, posted by:
* Paul_A_Suhler at
According to SMC, if MChngr is 1, then both SSC (for a tape) and SMC
commands are handled by the LU being queried.  This is an "attached medium

If Mchngr is 0, then that LU accepts only the commands of the base device
type, and another LUN accepts the SMC commands.  Typically, LUN 0 is the
tape drive and LUN 1 is the loader.  LUN 1 will also have MChngr of 0.
This is an "independent medium changer."



"Peter Wieland (Exchange)" <peterwie at> on 99/10/15

To:   "'roweber at'" <roweber at>, "T10, Reflector" <T10 at>
cc:   Paul A Suhler

Subject:  RE: SCSI Surrogate Mode?

i just want to make sure i understand what SPC has defined for embedded

i have a logical unit which accepts disk commands (and coincidentally has
the disk device type, what luck :).  If it also has an embedded media
changer in it then that LU sets the MChngr bit to indicate that it could
also accept media changer commands?  or does the bit indicate that there is
a second LUN on the "target" which supports MC commands?


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