Sense data and SCSI Good Status

Gerry.Houlder at Gerry.Houlder at
Thu Nov 1 06:51:08 PST 2001

* From the T10 Reflector (t10 at, posted by:
* Gerry.Houlder at

The wording you quote from SPC-3 applies specifically to a Request Sense
command. Thus a recovered error during processing (the standard prohibits
me from saying "execution") of the Request Sense command shall be ignored
the the requested sense data (presumably for a previous command that ended
with Check Condition status) shall be returned. The Good status of the
Request Sense command simply states that the requested sense bytes were
properly returned. If the Request Sense command itself ended with Check
Condition status, the standard warns that any returned data is invalid. It
should also warn that the previous sense bytes are probably lost and a new
Request Sense command that ends with Good status will return sense bytes
that describe the problem with the previous Request Sense (that had Check
Condition) rather than the original problem.

In the past there have been things in sense data that could be polled for.
There is a tape specific bit that was used in this way and a previous Check
Condition on a command was not required to see this status. Anything that
is designed to work this way bends (some will say breaks) the rules of the
standard and has to be done with polled Request Sense commands and NEVER

"Dave Peterson" <dap at> on 10/31/2001 02:48:39 PM

Sent by:  owner-t10 at

To:   "T10 Reflector" <t10 at>

Subject:  Sense data and SCSI Good Status

* From the T10 Reflector (t10 at, posted by:
* "Dave Peterson" <dap at>
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).

In SPC-3 text for the REQUEST SENSE command states:
"If a recovered error occurs during the processing of the REQUEST SENSE
command, the device server shall
return the sense data with GOOD status. If a device server returns CHECK
SENSE command, the sense data may be invalid."

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
where a REQUEST SENSE command has been issued for some reason.


David A. Peterson
Cisco Systems, Inc.
Lead Architect
Standards Development/Technical Marketing
6450 Wedgwood Road
Maple Grove, MN 55311
Email: dap at
Cell: 612-802-3299
Office: 763-398-1007

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