Reserve and Release for printers and comm devices

Hallam, Ken MV KHallam at
Mon Feb 5 09:51:00 PST 1996

* From the SCSI Reflector, posted by:
* "Hallam, Ken                 MV" <KHallam at>

The old style RESERVE/RELEASE commands should NOT be made mandatory for any 
devices.  This is a case of accepted practice in the industry being 
completely contrary to what Ted is asking for. The old RESERVE-RELEASE 
commands were poorly architected for the multiple Initiator environment. 
 One reason Unisys doesn't implement these commands on printers, tapes and 
other devices is that we always use multiple initiators and our I/O control 
software takes care of ownership and device physical condition status 
because we found the RESERVE/RELEASE function as described in SCSI-2 to be 
inadequate. Backing these old commands into mandatory status in SCSI-3 will 
cause untold problems with existing hardware and software and massive 
problems in customer sites, (not something we look forward to). I can't 
believe we are the only people who find this proposal repugnant. Let's let 
the new PERSISTENT RESERVATION commands be emphasized as the prefered way to 
implement a reservation function and not force us backwards in SCSI-3 to a 
command set with fundamental problems that few people have even implemented.

 I want to make it clear that Unisys will oppose this proposal.

Ken Hallam
Unisys SSD Engineering
ken.hallam at
From: scsi-owner
To: scsi
Subject: Reserve and Release for printers and comm devices
Date: Monday, January 15, 1996 9:43AM

* From the SCSI Reflector, posted by:
* <tedl at Exabyte.COM>
          To:    SCSI Reflector
          From:  Ted Lappin
                 tedl at
                 (303) 417-7718

          When editing the SSC document, I discovered that the reserve
          and release commands were optional for printers and not
          mentioned for communications devices.

          I propose that reserve and release (ordinary, SCSI-2 style,
          not persistent and no extents) be mandatory for SCSI-3
          printers and communications devices.

          Both of these device models are part of the stream class of
          devices which have an implicit state based on previous
          commands.  To allow proper control of these devices in
          multi-initiator environments, reserve and release are
          required.  Therefore, I believe that these commands should
          be mandatory.

          Does anyone else have an opinion on this, particularly to
          the contrary?  I would appreciate input from you or anyone
          you know, particularly implementers of SCSI printer or
          communication devices.

          Thank you.

More information about the T10 mailing list