SAS NOTIFY (RESERVED 2) encoding problem and arbitration fairness issue for an absurd case

Elliott, Robert (Server Storage) Elliott at hp.com
Fri Mar 14 16:34:32 PST 2003


* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert (Server Storage)" <Elliott at hp.com>
*
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We noticed two problems in sas-r03e this week:=20

1.  NOTIFY (RESERVED 2) is supposed to be neutral disparity but is not.
All the other ALIGNs and NOTIFYs are neutral.  A different encoding =
will
need to be assigned or this primitive will need to be removed.

2. One of the current arbitration fairness rules in 7.12.3 (Arbitration
fairness) is:
"If two connection requests pass on a physical link, the winner shall =
be
determined by comparing OPEN address frame field values in the =
following
order:

1) largest arbitration wait time field value; and=20
2) largest source sas address field value."=20

If two phys in a wide-capable port are attached to each other (unusual
but allowed) and for some reason they choose different connection rates
(not disallowed) when simultaneously sending OPENs, they need to agree
on which request wins.  If each phy assumes it wins and send
OPEN_ACCEPT, one phy would think the connection rate is different from
the other.

Adding:=20
3) largest connection rate field value.=20

solves this, and makes the comparison exactly the same as that used by
expander devices when comparing competing path requests (see 7.12.4.1
[Expander] Arbitration overview).


If there is no objection I'll add these to the letter ballot comments
and resolve them.=20
--=20
Rob Elliott, elliott at hp.com=20
Hewlett-Packard Industry Standard Server Storage Advanced Technology=20
 <https://ecardfile.com/id/RobElliott>
https://ecardfile.com/id/RobElliott=20




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SAS NOTIFY (RESERVED 2) encoding problem and arbitration = fairness issue for an absurd case We noticed two problems in sas-r03e = this week: 1.  NOTIFY (RESERVED 2) is = supposed to be neutral disparity but is not.  All the other ALIGNs = and NOTIFYs are neutral.  A different encoding will need to be = assigned or this primitive will need to be removed. 2. One of the current arbitration = fairness rules in 7.12.3 (Arbitration fairness) is:
 ;If two connection requests pass on a physical link, the winner = shall be determined by comparing OPEN address frame field values in the = following order: 1) largest arbitration wait time field = value; and 
2) largest source sas address field = value.; If two phys in a wide-capable port are = attached to each other (unusual but allowed) and for some reason they = choose different connection rates (not disallowed) when simultaneously = sending OPENs, they need to agree on which request wins.  If each = phy assumes it wins and send OPEN_ACCEPT, one phy would think the = connection rate is different from the other. Adding: 
3) largest connection rate field = value. solves this, and makes the comparison = exactly the same as that used by expander devices when comparing = competing path requests (see 7.12.4.1 [Expander] Arbitration = overview). 
If there is no objection I'll add = these to the letter ballot comments and resolve them. 
-- 
Rob Elliott, elliott at hp.com 
Hewlett-Packard Industry Standard = Server Storage Advanced Technology 
https://ecardfile.com/id/RobElliott 


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