SAS wide init/targ command transfers
Elliott, Robert (Server Storage)
Elliott at hp.com
Tue Jun 6 12:00:22 PDT 2006
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There are some restrictions in 220.127.116.11.6 PL_OC2:Over_Control state frame
transmission for task management functions. A SAS port does not send a task
management function that might affect a command that is in flight.
There is no specific advice about waiting to send commands that may affect
or depend on other commands that are also in-flight. This includes:
- command with the ORDERED or HEAD OF QUEUE task attribute
- PERSISTENT RESERVE OUT command with the PREEMPT AND ABORT service action
(aborts tasks already in the task set, if they've arrived yet)
If you send one of these in a connection before the ACK was received for the
previous command (in its connection), there is no guarantee which one the
device server will receive first.
Since a narrow port or a wide ports in only one connection at a time to
another port already preserves ordering (due to the interlocked frame
transmission rules), it's probably best for SAS-2 to include rules for these
cases for wide ports with multiple connections to other wide ports as well.
Rob Elliott, elliott at hp.com
Hewlett-Packard Industry Standard Server Storage Advanced Technology
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Mignon
Sent: Tuesday, June 06, 2006 4:58 AM
To: t10 at t10.org
Subject: SAS wide init/targ command transfers
Based on how I understand the spec (sas1r10), it is possible for a wide
Initiator and a wide Target to have simultaneous connections with each other
on different PHYs.
For this scenario (a wide initiator having multiple simultaneous connections
with a wide target), I could not find the info in the spec the rules or the
restrictions of command transfer/processing (e.g. if only simple commands
can be transmitted etc..). Can there be a case where a wide initiator sends
an ordered command on one phy and another ordered command on another phy to
the same wide Target?
Thanks in advance,
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