Transports per physical phy

Gerry.Houlder at Gerry.Houlder at
Thu May 1 06:40:19 PDT 2008

* From the T10 Reflector (t10 at, posted by:
* Gerry.Houlder at
Also remember that Rob is talking about concurrent usage. A host system
might have SSP, STP, and SMP layers that have access to the same logical
phy , but only one can have a connection at a given time. There are
different parts of the draft standard that discuss "what components can
exist" versus "what components can be active in particular connection".
	     "Elliott, Robert						   
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				       RE: Transports per physical phy	   
	     04/30/2008 06:38						   
There should be one TT and one MT per SAS logical phy.	An 8-wide HBA with
multiplexing can have connections open to 16 STP or SMP targets at the same
time.  Although the diagram otherwise recognizes the logical phy concept,
that statement is still broken.
If a connection is already open to STP target N and a connection request
comes in from STP target N, something is wrong - multiple connections for
one I_T nexus in STP is not allowed.  If a connection request comes in from
an SMP target, something is wrong - they are not supposed to send
connection requests.
Rob Elliott, HP Industry Standard Server Storage
From: Bill.Martin at Emulex.Com [mailto:Bill.Martin at Emulex.Com]
Sent: Wednesday, April 30, 2008 6:12 PM
To: Elliott, Robert (Server Storage); t10 at
Subject: Transports per physical phy
In figure 29 of SAS-2, there is a statement at the bottom of the figure of
“One or more SAS phys (with matching number of TTs and MTs) per SAS port”
This implies that there is only one STP or SMP transport layer per physical
phy.  Is that the intent of this diagram, and what is the response if there
is one STP or SMP connection on one logical phy when a second connection
request comes in on the other logical phy of this physical phy?  This is
analogous to multiple connection requests on multiple physical phys (which
might be part of a single wide port).  In the later case the request would
be rejected by the STP or SMP layer, not at the port layer.
I am not sure if the diagram needs to be corrected or if there is some
other answer already available in the specification.
Bill Martin
Office of Technology
Industry Standards
916 772-3658
916 765-6875 (Cell)
bill.martin at
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