[SAS] Who should receive CHANGE

Seto, Pak-lung pak-lung.seto at intel.com
Fri Oct 18 11:29:45 PDT 2002


* From the T10 Reflector (t10 at t10.org), posted by:
* "Seto, Pak-lung" <pak-lung.seto at intel.com>
*
Yes, target (disk)has decided not to support SMP, but regardless whether
target
will support SMP or not, target needs to know if there is something happened
on one of the links that it needs to make connection back to the initiator.

If the initiator send a command (read in this case) to the target.  The
target needs to remember
the "link rate" (which should define as end-to-end link rate) in the OPEN
Address
Frame in order to reconnect back to the initiator to deliver data when it is
ready.  What happen
if one of the link between the initiator and the target got reset and
re-negotiate
to a lower link speed which happens to be the new "end-to-end link rate"
between
that initiator and the target".  Now the "end-to-end link rate" saved by the
target
which was suppose to be used to reconnect back to the initiator become
invalid.
Therefore, the target needs to know something has happened to "a" link and
since
target does not support SMP, it has to assume all the saved link rate may no
longer valid
and since it is the target's turn to return data back to the initiator (in
this example).  The target
needs to play it safe to temporary use the minimum link rates as defined by
the SAS
standard to reconnect back to the initiator until the initiator initiate a
new connection
to the target to send the target the new "end-to-end link rate" thru the
OPEN Address Frame.
The target will need to do that for all initiator that it has outstanding
command to return data to.
This has been described somewhat in detail in another reflector message that
I sent earlier.

There can be different ways to handle this situation, but all of them
require the target to know
that it's saved "end-to-end link rate" may no longer valid.

Pak

-----Original Message-----
From: Reif, Jim [mailto:Jim.Reif at hp.com]
Sent: Friday, October 18, 2002 12:00 PM
To: Seto, Pak-lung
Subject: RE: [SAS] Who should receive CHANGE


Why do you feel that targets need to see the CHANGE primitive?

They will see them because the Expander will send out to all ports
regardless of the attached device type. But what would it do with
the information, since targets don't support SMP protocol?

Jim Reif
Hewlett-Packard 
281-514-8237
email: jim.reif at hp.com


-----Original Message-----
From: Seto, Pak-lung [mailto:pak-lung.seto at intel.com]
Sent: Friday, October 18, 2002 9:36 AM
To: 't10 at t10.org'
Subject: [SAS] Who should receive CHANGE


* From the T10 Reflector (t10 at t10.org), posted by:
* "Seto, Pak-lung" <pak-lung.seto at intel.com>
*
in SAS spec. v 2a page 107, Table 32

CHANGE primitive only send from E to I

but in clause 7.1.4.4, page 115

"CHANGE is sent by and expander device to notify initiator ports and other
expander devices that s configuration change has occurred."



Which one is correct?

I believe the CHANGE primitive needs to send to both expander devices and
targets also.

Pak
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