[T10] Question: About the number of identify

Ralph Weber roweber at ieee.org
Mon Feb 29 19:27:57 PST 2016

I am not an SPL expert, but maybe one is not needed here.

Based on SPL-4 r06, subclause "State description" provides a 
strong hint as to what is expected.

"Upon entry into this state, this state shall send either one or three 
Transmit IDENTIFY Address Frame
messages to the SL_IR transmitter.

"NOTE 30 - Phys compliant with SAS-1.1 only transmitted one Transmit 
IDENTIFY Address Frame message."

Thus, compliance with SAS-1.1 requires the sending of only one IDENTIFY 
Address Frame ...

By implication, SAS-2 and later might have a preference for sending 
three IDENTIFY Address Frame ... s ...
but this author cannot find any explicit statement to this effect in a 
wide variety of standards than have been investigated (including the 
SAS-2 revision in which the "one or three" wording first appeared).

The cited text can be traced back to T10/07-090r3 which was incorporated 
in SAS-2 r13 in November 2007.

T10/07-090r3 contains one page of introductory text in which includes 
the following sentence: "To better tolerate single-bit errors, the 
IDENTIFY address frame should be sent 3 times rather than just 1 time."

See: http://www.t10.org/cgi-bin/ac.pl?t=d&f=07-090r3.pdf

Note: The proposal's introduction is not now (and as far as I can tell, 
never has been) part of any SAS or SPL standard.

I leave it to the SPL wizards to decide whether valuable information in 
T10/07-090r3 is already in SPL-4 or even needs to be in SPL-4.

All the best,


On 2/26/2016 1:35 AM, Guojian (F) wrote:
> Hi,
> We know that identify frame can be sent one or three to the other side 
> after speed negotiation completed.
> What I want to know is what is the consideration? Just ensure the 
> other side can receive identify?
> Is there any chance that a SAS PHY will miss the first identify frame?
> Now I met a issue. When the host send just one identify frame, the HDD 
> will occur receiving identify expired with little probability. This 
> issue will be fixed when the host send three identify frame.
> Jason
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