Reserve and Release for printers and comm devices
Hallam, Ken MV
KHallam at po2.mv.unisys.com
Mon Feb 5 09:51:00 PST 1996
* From the SCSI Reflector, posted by:
* "Hallam, Ken MV" <KHallam at po2.mv.unisys.com>
*
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 mv.unisys.com
----------
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
Exabyte
tedl at exabyte.com
(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.
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