SAS NOTIFY (RESERVED 2) encoding problem and arbitration fairness issuefor an absurd case
gop at us.ibm.com
Mon Mar 17 06:55:32 PST 2003
* From the T10 Reflector (t10 at t10.org), posted by:
* George Penokie <gop at us.ibm.com>
I see no problem with what you are requesting, but we should talk about it
in a conference call.
Bye for now,
Dept 2C6 114-2 N212
E-Mail: gop at us.ibm.com
External: 507-253-5208 FAX: 507-253-2880
(Server Storage)" To: <t10 at t10.org>
<Elliott at hp.com> cc:
Sent by: Subject: SAS NOTIFY (RESERVED 2) encoding problem and arbitration fairness issue for
owner-t10 at t10.org 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
"If two connection requests pass on a physical link, the winner shall be
determined by comparing OPEN address frame field values in the following
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.
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 18.104.22.168
[Expander] Arbitration overview).
If there is no objection I'll add these to the letter ballot comments and
Rob Elliott, elliott at hp.com
Hewlett-Packard Industry Standard Server Storage Advanced Technology
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