SSC/SMC wg minutes, 9/14/95, SoftWriteProt.
patrick.mercer at syquest.com
Tue Sep 19 09:49:41 PDT 1995
Date: Sep. 19, 1995
To: SSC/SMC, SBC and SPC Working Groups
From: Pat Mercer
Subject: SCSI-3 Software Write Protect proposal
This is a proposal to add the Software Write Protect, as defined
in SSC, to either SBC or SPC.
(SSC: SCSI Stream Commands
SBC: SCSI Block Commands
SMC: SCSI Media Changer Commands
SPC: SCSI Primary Commands)
The SSC/SMC WG 11/14 minutes indicated that "the Prevent/Allow
Media Removal command should be in the SPC document as it can be
used by tape, disk and CD rom devices."
I would like to suggest that the same situation applies to the
Software Write Protect function. This function is applicable to
both tape and disk drives, and is specifically a desirable feature
for removable media disk drives.
It is unfortunate that I was not able to attend the meeting and
bring this up earlier, before the control bit was moved, as
indicated by the SSC/SMC WG 11/14 minutes, which contain:
> 4.5 - Initiator controlled write protect. (X3T10/95-134r0)
> Arlan proposed that the Software Write Protect bit be moved from
> the read-write error recovery mode page to the device configuration
> mode page. Ted suggested bit 2 of byte 10 for this use. The
> working group recommended that this be approved by the Plenary.
I propose that Software Write Protect be specified for both tapes
and disks. I would appreciate some advice, though, as to how it
should be done. I see several possibilities:
--1. Restore the SWP control bit to the SSC Read-Write Error
Recovery Mode page, and add the SWP bit at the same location to
the SBC page.
A possibility, then, would be to combine the pages, which are
compatible and have no conflicts, if the various SBC fields are
allowed to be left unused by SSC, and move the results into SPC.
I'm not clear if the SBC and SSC specific fields could be
detailed in SPC, if they should be listed in SBC and SSC or if
the slightly different page definitions should just be left in
SBC and SSC.
--2. Leave SSC as is and add a Device Configuration page to
SBC, using the SSC location for the SWP bit (Byte 10, bit 2).
The rest of the page would be empty. This is easy for SSC
but doesn't seem the best for SBC.
--3: Leave SSC as is and add the SWP bit to the SBC Read-Write
error recovery Mode page where it was in SSC. This would work
for both but would result in the same bit defined in two
different pages, which doesn't seem too great.
--4: ??? Handle this some other way.
Suggestions would be most welcome.
I appreciate your consideration, and please add this as an
agenda item for the Palm Springs meeting for SSC, SBC and,
if appropriate, SPC.
SyQuest Technology, Inc.
47071 Bayside Parkway
Fremont, CA 94538-6517
Phone: 510-226-4215 FAX: 510-226-4104
Email: patrick.mercer at syquest.com
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