Multiple connections or I_T_x_x nexus

Chris.Malakapalli at seagate.com Chris.Malakapalli at seagate.com
Tue Feb 25 12:16:38 PST 2003


* From the T10 Reflector (t10 at t10.org), posted by:
* Chris.Malakapalli at seagate.com
*


I understand now that within the same I_T nexus, different L_Q connections
can exist concurrently on wide ports but wondering about the different
initiator ports connecting to the same wide target port. If you look at the
case b of page 35, section 4.1.9, rev.3d, it is specifically talking about
concurrent connections with two different initiator ports connecting with
the same wide target port. Figure 20 seems to suggest this is possible but
some clarification would be appreciated.

Chris Malakapalli
Seagate Technology




                                                                                                                                      
                      "Sheffield, Robert                                                                                              
                      L"                          To:      <Chris.Malakapalli at seagate.com>, <t10 at t10.org>                             
                      <robert.l.sheffield         cc:                                                                                 
                      @intel.com>                 Subject: Re: Multiple connections or I_T_x_x nexus                                  
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* From the T10 Reflector (t10 at t10.org), posted by:
* "Sheffield, Robert L" <robert.l.sheffield at intel.com>
*
On any connection request the expander devices are free to select the
pathway, including the choice of phy at the destination. The originator of
the open doesn't need to determine which phy to open, only that there's a
reasonable chance that there's another pathway available. And yes, these
connections can be active at the same time.

Bob
-----------------
Sent from my BlackBerry Handheld.

-----Original Message-----
From: Chris.Malakapalli at seagate.com <Chris.Malakapalli at seagate.com>
To: t10 at t10.org <t10 at t10.org>
Sent: Tue Feb 25 08:20:54 2003
Subject: Multiple connections or I_T_x_x nexus

* From the T10 Reflector (t10 at t10.org), posted by:
* Chris.Malakapalli at seagate.com
*
I have somewhat a related question to the wide port question posted
earlier. Under section 4.1.9 of SAS rev 3d , page 35, case b states with
reference to Fig. 20 that:

"the connections labeled A and C are an example of one target port with
connections to multiple initiator ports" ...

The question is can these connections be concurrently active to support two
separate I_T_x_x nexus? Given that there is no provision in the OPEN
address frame to specify which phy to use for the connection, my feeling is
they cannot be active at the same time, but am hoping someone could clarify
this for me.

Also, there seem to be other areas in the spec, where this subject is being
discussed. For instance, according to 7.11.1 on page 177,

"A wide port  may have separate connections on each of its phys"

Again, can these connections be active at the same? If not, is it true then
that a wide port can support only a single connection at a time and all
phys support that same connection, in which case, the above sentence could
be interpreted as misleading. In rev 3c, there was some discussion of
connection at a link layer (between the phys) and now in rev 3d, it appears
to have been removed.

Thanks for your help.

Chris Malakapalli
Seagate Technology


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