SCSI-3 Block Commands (SBC)

Gene Milligan Gene_Milligan at
Thu Aug 11 08:03:32 PDT 1994

Regarding Tewell's questions:
1. Should we divide the document into "sections" such as General
Block Commands, Commands for Direct Access Devices, Commands for
Write-Once Devices and Commands for Optical Memory Devices -OR-
should we simply annotate each command with the differences between
the device types.
 No to both. SBC is the command set for Direct Access Devices with a SAManized
name to confuse implementors. Special requirements for optical devices not
fitting the desired behavior of Direct Access Devices should be moved to
Multimedia Commands (MMC).
2. Should there be any verbiage describing suggested action to be
taken when optional bit(s) are set in the CDB of a mandatory command?
 Yes. They should be indicated as optional. Beyond that required action should
be described. The concept of  "suggested"  is a weakness of the committee which
just leads to incompatibilities at the worst and wasted description at the
best. Requirements should not be obfuscated by making them suggestions.
Optional does not mean vendor unique.
3. Is there any interest in adding a definition for an optional
Scatter Write/Gathered Read command to speed up the access of
'logically tied' blocks of data on a device that might be physically
disjoint on the media. This would allow for very quick reading and
writing of fragmented files on the disk.
 It depends upon the proposal. There was a proposal floated years ago in the
early days of SCSI -2 which was eventually withdrawn by the proposer. However
the editor of SBC should not insert new proposals into the document to see if
they are acceptable. Proposals should begin as free standing documents to be
voted in, modified, or voted down.
Thanks for the encouragement.
Gene Milligan
Gene Milligan -- Gene_Milligan at
Seagate Technology   -   920 Disc Drive   -   Scotts Valley, CA 95066 USA
Main Phone 408-438-6550   -   Email Problems postmaster at
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### OGATE Version 8 message trace and attachment information:
### MsgFileName: m:\mgate\outbound\447.MSG
### Org Date:    08-11-94 08:03:55 AM
### From:        Gene Milligan at SEAGATE
### To:          scsi @ @ internet
### Subject:     Re: SCSI-3 Block Commands (SBC)
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