SAS Wide link question

Wed Dec 18 07:56:01 PST 2002

* From the T10 Reflector (t10 at t10.org), posted by:
* "Sheffield, Robert L" <robert.l.sheffield at intel.com>
*
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Rob,
=20
Figure 17 in SAS-r03 shows two expander ports attached to two initiator
ports (A,B) and (C,D,E,F). I'm wondering how the expander knows to
partition the ports that way. The Identify address frame reports the =
SAS
address of the "device". If this is taken literally, the same SAS
address would be reported by the initiator on all 6 phys. I assume if
the initiator wants the expander to recognize distinct ports it would
report the SAS addresses for the distinct 'ports' in the Identify
Address Frame, but I can't find anywhere in the standard where it says
so. As far as I can see, Expander Devices don't have SAS addresses for
their "ports", so the mapping of ports across phys in the expander
device must be based on information gathered from the attached
initiators and targets. Can you clarify this for me, or point me to a
place in the document that explains it?
=20
Thanks,
Bob
=20
Bob Sheffield
Intel Corporation - CH6-333
Storage Components Division (SCD)
5000 W. Chandler Blvd
Chandler, AZ 85226-3699
Phone: 480-554-8597
Fax: 480-554-6617

-----Original Message-----
From: Elliott, Robert (Server Storage) [mailto:Elliott at hp.com]
Sent: Wednesday, December 11, 2002 5:19 PM
To: t10 at t10.org
Subject: RE: SAS Wide link question

If the target port is wide (i.e. it has more than one phy, advertising
the same SAS address), it may request a connection using any phy in the
wide port.  It doesn't have to remember the phy through which the
command arrived.
=20
Similarly, a wide initiator port may request a connection to a target
using a different phy than it has used previously.
=20
Expanders are also free to choose any link in a wide link as they route
connection requests through the domain.
=20
A wide initiator port should not ask for more than one connection at a
time to the same target port unless it knows the target port is also
wide (otherwise, all but one of its requests will lose arbitration to
the winner).
--=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

-----Original Message-----
From: Kevin_Marks at Dell.com [mailto:Kevin_Marks at Dell.com]=20
Sent: Tuesday, December 10, 2002 1:20 PM
To: t10 at t10.org
Subject: SAS Wide link question

With an initiator and target in a SAS domain having a wide link
configuration, on a reconnect does the target for example have to
maintain allegiance to the original path (phy) when reconnecting or can
arbitrate for any path back to the initiator.

=20

Thanks

=20

Kevin

=20

Kevin Marks ( Kevin_Marks at Dell.com <mailto:Kevin_Marks at Dell.com>  )
=20

=20

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 Figure=20 17 in SAS-r03 shows two expander ports attached to two initiator ports = (A,B) and=20 (C,D,E,F). I'm wondering how the expander knows to partition the ports = that way.=20 The Identify address frame reports the SAS address of the "device". If = this is=20 taken literally, the same SAS address would be reported by the = initiator on all=20 6 phys. I assume if the initiator wants the expander to recognize = distinct ports=20 it would report the SAS addresses for the distinct 'ports' in the = Identify=20 Address Frame, but I can't find anywhere in the standard where it says = so. As=20 far as I can see, Expander Devices don't have SAS addresses for their = "ports",=20 so the mapping of ports across phys in the expander device must be = based on=20 information gathered from the attached initiators and targets. Can you = clarify=20 this for me, or point me to a place in the document that explains=20 it?

 Thanks,
 Bob

 Bob Sheffield
Intel Corporation - = CH6-333
Storage=20 Components Division (SCD)
5000 W. Chandler Blvd
Chandler, AZ=20 85226-3699
Phone: 480-554-8597
Fax:=20 480-554-6617

 -----Original Message-----
From: Elliott, Robert = (Server=20 Storage) [mailto:Elliott at hp.com]
Sent: Wednesday, December = 11, 2002=20 5:19 PM
To: t10 at t10.org
Subject: RE: SAS Wide = link=20 question

 If=20 the target port is wide (i.e. it has more than one phy, advertising = the same=20 SAS address), it may request a connection using any phy in the wide=20 port.  It doesn't have to remember the phy through which the = command=20 arrived.

 Similarly, a wide initiator port may request a connection to = a target=20 using a different phy than it has used = previously.

 Expanders are also free to choose any link in a wide link as = they route=20 connection requests through the domain.

 A=20 wide initiator port should not ask for more than one connection at a = time to=20 the same target port unless it knows the target port is also wide = (otherwise,=20 all but one of its requests will lose arbitration to the=20 winner).
 -- = 
Rob Elliott, = elliott at hp.com=20 
Hewlett-Packard = Industry Standard=20 Server Storage Advanced Technology 
https://ecardfile.com/id/Ro= bElliott=20 

-----Original Message-----
From:=20 Kevin_Marks at Dell.com [mailto:Kevin_Marks at Dell.com] 
Sent: = Tuesday,=20 December 10, 2002 1:20 PM
To: = t10 at t10.org
Subject: SAS=20 Wide link question

 With an initiator and = target in=20 a SAS domain having a wide link configuration, on a reconnect does = the=20 target for example have to maintain allegiance to the original path = (phy)=20 when reconnecting or can arbitrate for any path back to the=20 initiator. Kevin Marks ( Kevin_Marks at Dell.com=20 )