The current standard does not allow two
logical phys to be represented as different ports, by reporting different SAS
addresses. This operation would add significant complexity that should not be
incorporated into the standard. I would like to see justification of why this
would be useful, and a proposal of how it would be incorporated, including how
it would be discovered that these two logical ports are part of a single
physical port.
Bill Martin
Emulex
Office of Technology
Industry Standards
916 772-3658
916 765-6875 (Cell)
bill.martin@emulex.com
From:
owner-t10@t10.org [mailto:owner-t10@t10.org] On
Behalf Of
Sent: Monday, May 07, 2007 4:25 PM
To: Day, Brian;
craig@expertio.com; t10@t10.org
Subject: RE: SAS 2 Muxing and
DISCOVER
Craig and
Brian,
Saw my name
mentioned in this thread. I think what's being suggested is that it might be a
reasonable thing for logical phys to be in different SAS ports, even if they
share the same physical phy. This would require changing the standard, andI
haven't heard a good argument to say why it wouldn't work. Nobody has posted a
proposal showing the changes that would allow this.
Bob Sheffield
Intel
Corporation
From:
owner-t10@t10.org [mailto:owner-t10@t10.org] On
Behalf Of Day, Brian
Sent: Monday, May 07, 2007 3:28 PM
To: craig@expertio.com;
t10@t10.org
Subject: RE: SAS 2 Muxing and
DISCOVER
Craig...
Actually, the current 9a draft of the
spec (it was also present in revision 9) does require all logical phys/links
for a physical phy/link have the same SAS address. The statement is in
section 7.8.2, saying:
"The IDENTIFY address frame sent by
each logical phy in a physical phy shall be identical."
Based on that requirement, logical links
within a muxxed physical phy would then always be in the same wide port.
And provides a reason that keeping the
discovery based on physical phys is sufficient.
Brian Day
LSI Corp.
From: Craig
Stoops [mailto:craig@expertio.com]
Sent: Sunday, May 06, 2007 10:09
AM
To: t10@t10.org
Cc: Day, Brian; '
Subject: FW: SAS 2 Muxing and
DISCOVER
Rob (Elliot),
I don't think anyone responded to this. I
have seen several proposals (one from Robert Sheffield) that discuss
handling of virtual phys (in an expander) but none talking about logical phys
that have been created by the addition of muxing.
Logical phys for a physical link need not
have the same address, and may or may not be part of the a wide port.
Does anyone have a proposal on how this
(discover and reporting) should be handled?
Thanks,
Craig
-----Original Message-----
From: Craig Stoops
[mailto:craig@expertio.com]
Sent: Wednesday, March 14, 2007
8:11 PM
To: 't10@t10.org'
Subject: SAS 2 Muxing and DISCOVER
Rob, Steve, Brian and others involved:
I'm wondering about SMP Discover and interaction with
Muxing. I've read the recent proposal 07-091r0 regarding the Discover
extensions, but I feel there are some issues at hand.
From a higher perspective, there isn't much difference
between 2 logical phys with muxing and 2 physical phys. Each logical phy sends
and receives an Identify Frame (IAF). As such, each logical phy is free to
advertise any capabilities it sees fit, including a unique SAS address. The two
logical phys need not send the same information. The net result is, that the 2
related logical phys may either be viewed as 2 logical ports, or two phys as
part of a wide port. I know that when Muxing was suggested that being seen as a
wide port is what was in mind, but I can think of several target devices that
would like to advertize two different SAS addresses on the muxed link. There is
nothing I can find in the standard to prevent this, and modeling show it works
very nicely.
To the higher level layers such as port layer of Expander
Function, there is no difference between a muxed link and a non-muxed link.
Only the SAS addresses on that link determine whether the logical phy is part
of a wide port or not.
However, this implies that when addressing a SAS device
that has muxing enabled, that it should report the number of phy as as the
number of logical phys, not physical. And also, it needs to be possible to
issue a Discover to each logical phy, not just physical phy inorder to gain
access to the individual IAF results.
Another potential solution is to issue Discover for Phyical
phys, but have space to report the capabilities of each logical phy that is
part of that phycial phy, eg two attached sas address, two sets of capbiltiies
(both local and remote), etc
Comments?
Craig Stoops
ExpertIO, Inc.
"Your Storage Verification and Design Experts"
805-428-0839