[T10] Tape Stream Miroring incorporation into SPC-5 r11 feedback ... "shall direct"

Ralph Weber roweber at ieee.org
Mon Aug 8 02:50:04 PDT 2016

Regarding the discussion of "the copy manager shall and the device 
server shall" detailed below ...

The change currently identified for inclusion in SPC-5 r12 is to delete 
the first shall.

This particular change has several advantages.

  * It is one of the changes proposed during the discussion of the
    comment reproduced below.
  * As a one-word change, it is the smallest possible change mentioned
    during the discussion.
  * The change seems to address the oldest outstanding comment, i.e.,
    "something is missing".
  * The resulting text identically matches the last sentence in the
    cited paragraph, and that sentence generated no comments.

The suggestion that the original text be reinstated deserves a response, 
and that response follows.

There are substantial risks associated with asking any T10 editor to 
incorporate the first-ever usage of a particular word, and this was the 
initial problem with the phrase "the copy  manager shall direct the 
device server to".

Today, the word "direct" is **never** used as a verb in SPC-5. The only 
SPC-5 usage of "direct" is in compound names, e.g., direct-access block 
device and direct access memory.

A recourse to non-traditional phrasing typically masks an attempt to 
violate some long-standing precept of SCSI standards. With this alert in 
mind, finding the technical flaw in the original text becomes a cakewalk.

Great effort has been expended throughout SAM-x and SPC-x to avoid 
defining the details of interactions between copy managers and device 
servers. For many years, the goal has been to achieve the greatest 
possible flexibility of copy manager product designs. Generally 
speaking, minimizing explicit requirements on inside-the-device 
interactions has been used to achieve this goal.

This decision became the agreed practice after a half-day debate over 
whether commands flow through the device server to the copy manager or 
go directly to the copy manager. Eventually, it became obvious that the 
choices were silence on the subject or using the lunch hour to setup a 
mud wrestling pit between the head tables.

As a defense against future letter ballot comments, therefore, the 
editor respectfully insists that the only way to restore the original 
wording is through a CAP-approved proposal which makes only that change. 
Should this event come to pass, the proposal's number (and the vote 
tally approving it) will be noted for inclusion in responses to the 
all-but-certain letter ballot comments on the sole use of the "direct" 
verb in SPC-5.

All the best,


On 8/3/2016 9:32 PM, Dennis Appleyard wrote:
> Kevin,
> Thanks for the review.
> My comments are inline below.
> Dennis
> On 8/1/2016 1:09 PM, Kevin D Butt wrote:
>> Ralph, Dennis, and all,
>> <snip>
>> *Strictly incorporation issues:*
>> <snip>
>> On page 281, fourth paragraph, "then the <<copy manager shall and 
>> device server shall>>establish a
>> deferred error condition with CHECK CONDITION status" I think there 
>> is something wrong with "copy manager shall and device server shall" 
>> The device server is the one to establish a deferred error. The copy 
>> manager has a requirement to terminate the copy operation which was 
>> just stated prior to the then, so what does the copy manager need to 
>> do here? I think, perhaps, the "copy manager shall and" should be 
>> deleted, but perhaps there was intent to have something here.
> I suggest changing to "then the copy  manager shall direct the device 
> server to establish a deferred error condition" This was the wording 
> in the proposal.
>> *Other issues:*
>> <snip>

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