RBC delays op x12 Inquiry?

Pat LaVarre LAVARRE at iomega.com
Tue Mar 12 12:28:41 PST 2002


* 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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