MMC WG Meeting Announcement: 15 January 2003

Elliott, Robert (Server Storage) Elliott at hp.com
Thu Jan 9 15:25:40 PST 2003


* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert (Server Storage)" <Elliott at hp.com>
*
 >  7.0 New Business 
 >  Review the MMC-4 draft revision 1f.
 
I notice that mmc4r01f includes sections defining commands that have a
home in other standards (especially SPC-3 commands like INQUIRY, REQUEST
SENSE, TEST UNIT READY, MODE SENSE, MODE SELECT, READ BUFFER, and WRITE
BUFFER); these were not in mmc3.  I think this is a mistake.  If a
correction is made in SPC-3, it's not going to be automatically tracked
in MMC-4, and vice-versa.

For example, in the INQUIRY command, SPC-3 recently grew the ALLOCATION
LENGTH field to 2 bytes from 1 byte; MMC-4's version still only shows
one byte.  SPC-3 is obsoleting references to asynchronous event
reporting, but MMC-4 still references those bits.  SPC-2 defined
"version descriptors" in bytes 56-95, while MMC-4 shows them as
reserved.  

If MMC-4 needs to "profile" those commands, I think it can so without
appearing to redefine any of the fields.  Don't show the CDB format;
just include a table with the fields of interest and provide comments on
the MMC-4 requirements for those fields.  For example, INQUIRY could
have a table listing:
PERIPHERAL DEVICE TYPE  00101b 
PERIPHERAL QUALIFIER    000b
RMB                     1
but leave it up to SPC-3 to define what those fields mean.  Don't even
mention fields like BQue and CmdQue where MMC-4 devices are free to
implement anything they want.

Some of the fields marked as "shall be 0" in the current draft seem a
bit overreaching.  Why does MMC-4 need to prohibit an access control
coordinator, asymmetric logical unit access, or enclosure services from
coexisting in an MMC-4 logical unit?  

--
Rob Elliott, elliott at hp.com
Hewlett-Packard Industry Standard Server Storage Advanced Technology
https://ecardfile.com/id/RobElliott


*
* For T10 Reflector information, send a message with
* 'info t10' (no quotes) in the message body to majordomo at t10.org




More information about the T10 mailing list