reading blocks prior to a medium error

Penokie, George George.Penokie at lsi.com
Wed Dec 15 12:28:42 PST 2010


* From the T10 Reflector (t10 at t10.org), posted by:
* "Penokie, George" <George.Penokie at lsi.com>
*
This very topic was talked about in the last SCSI standards meeting in
November. The minutes from that discussion state:
5.2.7 SBC-3: Read data transferred on unrecovered error (yes-no-maybe?)
[Penokie]
George Penokie asked the group to consider whether the contents of the
Data-in Buffer are valid when an unrecovered error is reported. The group
suggested that George read the definition of the Data-in Buffer in subclause
5.1
of SAM-5.
George asked that this topic be removed from future agendas.
The wording being referenced in the minutes is:
Data-In Buffer: A buffer (see 5.4.3) to contain command specific information
returned by the logical unit by the time of command completion. The Execute
Command procedure call shall not return a GOOD status or CONDITION MET status
unless the buffer contents are valid. The application client shall treat the
buffer contents as invalid unless Execute Command procedure call returns a
GOOD status or CONDITION MET status. While some valid data may be present for
other values of status, the application client should rely on additional
information from the logical unit (e.g., sense data) to determine the state
of the buffer contents. If the command terminates with a service response of
SERVICE DELIVERY OR TARGET FAILURE, the application client shall consider the
buffer to be undefined
The net of all that is that no data from a read command should be considered
valid unless the command is successful.
Bye for now, 
George Penokie
LSI Corporation 
3033 41st St. NW 
Suite 100 
Rochester, MN 55901
507-328-9017 
george.penokie at lsi.com
-----Original Message-----
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Douglas
Gilbert
Sent: Wednesday, December 15, 2010 11:29 AM
Subject: sbc: reading blocks prior to a medium error
* From the T10 Reflector (t10 at t10.org), posted by:
* Douglas Gilbert <dgilbert at interlog.com>
*
When the TB bit is set in the Read-Write Error
Recovery mode page section 6.4.7 of sbc3r25.pdf
seems to imply that the good logical blocks
read prior to the unrecovered error will be
placed in the data-in buffer.
The TB bit only applies to the lowest numbered
LBA with an unrecovered error that is being read.
It seems counter intuitive to place that logical
block in the data-in buffer and not the good blocks
that precede it.
But I can't see the words that imply that the good
logical blocks prior to the unrecovered error will
be placed in the data-in buffer when the TB bit is
clear. Is this guaranteed?
Douglas Gilbert
*
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