RBC delays op x12 Inquiry?

Paul von Behren paul.vonbehren at sun.com
Tue Mar 12 13:38:52 PST 2002


* From the T10 Reflector (t10 at t10.org), posted by:
* Paul von Behren <paul.vonbehren at sun.com>
*
Look at SPC "Model common to all devices types" discussion
of Inquiry and Test Unit Ready (1 paragraph on each).  It
seems to have enough info to suggest that Test Unit Ready 
response should be immediate and Inquiry may take longer
if it relies on the underlying media.

Paul

Pat LaVarre wrote:
> 
> * From the T10 Reflector (t10 at t10.org), posted by:
> * "Pat LaVarre" <LAVARRE at iomega.com>
> *
> > > I see RBC strikes the phrase "the standard INQUIRY
> > > data should be available without incurring any media
> > > access delays" from the description of op x12.
> ...
> > all the force and majesty of a "should"
> 
> Offline, thank you again, I was kindly supplied with the anonymised explanation quoted below of when we may see -x 12 0 0 0 FF 0 -i xFF (Inquiry for up to xFF bytes) take significantly longer to complete than the Windows standard -x 12 0 0 0 24 0 -i x24 (Inquiry for up to x24 bytes).
> 
> Me, in bus traces, I see the "client application program[s] ... at the initiator" vary in whether they begin life with op x00 TestUnitReady or op x12 Inquiry.
> 
> I'd say devices that make op x12 Inquiry slow are in effect voting to begin life with op x00 TestUnitReady, in a de facto standard noone's bothered to write down.
> 
> Pat LaVarre
> 
> >>> [anonymised] 03/01/02 01:22PM >>>
> ... there is serial number data (for example) in some of the inquiry payloads - in vendor-unique areas (...?).  Thus, to get this data, they had to spin up hda's before responding to the inquiry. The spin up can sometimes take a few seconds to tens of seconds - and some initiators timed out on this basic command usually used at probe time.   So the recommendation is that if you asked for only enough inquiry data  to cover the standard data, then it would be a near-immediate response.
> ...
> 
> >>> Peter Johansson 03/01/02 11:07AM >>>
> * From the T10 Reflector (t10 at t10.org), posted by:
> * Peter Johansson <PJohansson at ACM.org>
> *
> At 10:36 AM 3/1/2002 -0700, Pat LaVarre wrote:
> 
> >I see RBC strikes the phrase "the standard INQUIRY data should be
> >available without incurring any media access delays" from the description
> >of op x12.
> 
> I go out on a bit of a limb to say this, Pat, since I don't have detailed
> notes from the RBC meetings. But I suspect it was eliminated in the spirit
> that it didn't have much to say in the first place. That is, it has all the
> force and majesty of a "should" ...
> 
> Another perspective is that it's not really a standards matter: if it's not
> sufficiently important to rise to the level of a "shall", market forces
> will determine whether the successful devices return as much data as they
> can as soon as they can---or not.
> 
> To put it another way, if you are designing a client application program to
> execute at the initiator, what possible difference would this
> RECOMMENDATION make to your design?
> ...
> 
> *
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