03-002r0: Remove SPI from SAM-3 and SPC-3 [a little bit more]

Sheffield, Robert L robert.l.sheffield at intel.com
Fri Feb 7 17:13:21 PST 2003


* From the T10 Reflector (t10 at t10.org), posted by:
* "Sheffield, Robert L" <robert.l.sheffield at intel.com>
*
Is the proposal really to remove ACA completely from SAM-3?

I can understand that with auto-sense there isn't a need to preserve the sense information for a subsequent REQUEST SENSE command, but I thought the intent of ACA went beyond just preserving sense data. In many cases an initiator may want to issue additional retry commands (rezero unit, retry the same command, read long, twiddle recovery mode pages to transfer the bad block,....), and needs to be able to execute these recovery procedures without worrying about interfering commands from other initiators. I can't say for certain that any existing drivers or storage controllers today use ACA to implement this type of recovery, but it's clear the intent of ACA originally was, in part, to address this sort of error recovery. These sorts of retry mechanisms would apply as well to SAS or fibre-channel FCP as they do for SPI, so I don't see the end of SPI itself as adequate justification for eliminating ACA.

Regards,
Bob Sheffield
Intel Corporation - CH6-333
Storage Components Division (SCD)
5000 W. Chandler Blvd
Chandler, AZ 85226-3699
Phone: 480-554-8597
Fax: 480-554-6617


-----Original Message-----
From: Ralph Weber [mailto:ralphoweber at compuserve.com]
Sent: Tuesday, January 07, 2003 8:31 PM
To: T10, Reflector
Cc: Elliott, Robert (Server Storage)
Subject: Re: 03-002r0: Remove SPI from SAM-3 and SPC-3 [a little bit
more]


* From the T10 Reflector (t10 at t10.org), posted by:
* Ralph Weber <ralphoweber at compuserve.com>
*
Rob,

I never suggested that REQUEST SENSE be made obsolete.
I am, however, questioning whether it needs to remain
mandatory for all device types.

I seriously doubt that any real world device will decline
to implement REQUEST SENSE anytime soon.

I do not have any serious problems with leaving REQUEST
SENSE mandatory for all device types, but I believe that
the result will be a profoundly lame explanation of why
in SPC-3 subclause 5.2.3 along the lines of the polling
function that you note.

This could be a case where we decide to make no changes
now and let time give us some perspective on the matter.
That is a fine way to go.

Regards,

.Ralph

Elliott, Robert (Server Storage) wrote:

> 
>* From the T10 Reflector (t10 at t10.org), posted by:
>* "Elliott, Robert (Server Storage)" <Elliott at hp.com>
>*
>There is one other SCSI transport that still uses contingent allegiance
>(CA): ATAPI (ATA Packet Interface, defined in T13's ATA/ATAPI standard).
>ATAPI devices will still require REQUEST SENSE, regardless of their
>command set (most likely but not exclusively MMC).  Perhaps that
>requirement could be documented in ATA/ATAPI-7 itself. 
>
>Many devices let applications poll with REQUEST SENSE to retrieve sense
>data containing progress indication - the status of long operations like
>FORMAT MEDIUM or self-test.  I don't think autosense can replace this
>usage.  REQUEST SENSE might only need to be required for devices
>implementing those commands, though.
>
>A quick web search shows at least one Fibre Channel driver might get
>upset if a target chose not to support autosense (but only after it had
>trouble delivering the autosense data in the first place):
>"The driver now issues a request sense when an FCP_RSP is received with
>check condition status, but no sense data (CR#3872)"
>
>--
>Rob Elliott, elliott at hp.com
>Hewlett-Packard Industry Standard Server Storage Advanced Technology
>https://ecardfile.com/id/RobElliott
>  
>


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