Sense data and SCSI Good Status

Peter Johansson PJohansson at acm.org
Wed Oct 31 13:37:06 PST 2001


* From the T10 Reflector (t10 at t10.org), posted by:
* Peter Johansson <PJohansson at ACM.org>
*
At 02:48 PM 10/31/2001 -0600, Dave Peterson wrote:

>If a recoverable error occurs for a command other than REQUEST SENSE, is 
>it valid to return sense data along with a Good SCSI status? (I'm looking 
>but have not yet found any text about this yet, but I'll keep looking).

I believe that GOOD status implies the absence of sense data.

>Thus for auto-sense protocols (e.g., iSCSI) it appears the spec needs to 
>specify sense data may be returned with a Good status, at least for the 
>case where a REQUEST SENSE command has been issued for some reason.

At least one autosense protocol, SBP, addresses this issue. See ANSI NCITS 
325-1998, Annex B.2. When SCSI status is GOOD, sense data is not returned.

Don't confuse sense data for the completed command with sense data that may 
be in the buffer provided when REQUEST SENSE is explicitly used to retrieve 
sense data. When REQUEST SENSE completes with GOOD status, there is no 
sense data returned pertinent to the REQUEST SENSE command itself---but any 
pending sense data has been transferred! A tricky point ...



Regards,

Peter Johansson

Congruent Software, Inc.
98 Colorado Avenue
Berkeley, CA  94707

(510) 527-3926
(510) 527-3856 FAX

PJohansson at ACM.org

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