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
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