Change count & Route Table clearing

Subramanian Kuppusamy, Noida subramaniank at noida.hcltech.com
Thu Sep 2 05:14:28 PDT 2004


* From the T10 Reflector (t10 at t10.org), posted by:
* "Subramanian Kuppusamy, Noida" <subramaniank at noida.hcltech.com>
*
 Thank you John for the immediate reply,
Still its not convincing
1.Checking Changecount value in all expanders is time consuming.
Since Steve Fairchild has included this check in Annex-K, I just wanted to
know whether there is any other significance for this check or can we
discard it.
Because Broadcast (Change) primitive will anyway reinitiate the discover
process.

2.Once connection is established, clearing the Route table should not affect
the traffic which is in progress. 
Moreover route table must be cleared before reconfiguring to avoid dead
entries. 
So a SMP Request function to clear the route table will make reconfiguration
clean and can save time.

Thanks for your time

Regards,
Subra

-----Original Message-----
From: owner-t10 at t10.org
To: Subramanian Kuppusamy, Noida; 't10 at t10.org '
Sent: 9/1/04 7:10 PM
Subject: RE: Change count & Route Table clearing

* From the T10 Reflector (t10 at t10.org), posted by:
* "Johnson, Stephen B." <Stephen.B.Johnson at lsil.com>
*
Please see below

-----Original Message-----
From: Subramanian Kuppusamy, Noida
[mailto:subramaniank at noida.hcltech.com]
Sent: Tuesday, August 31, 2004 8:05 PM
To: 't10 at t10.org '
Subject: Change count & Route Table clearing


* From the T10 Reflector (t10 at t10.org), posted by:
* "Subramanian Kuppusamy, Noida" <subramaniank at noida.hcltech.com>
*
Hi,
I am new to this group. I have some basic doubts in Annex-K of SAS 1.1
specs

1. If I correclty understood Changecount value is checked by the
intiator
only for the top most Expander or the Hub expander.
   From the specification,Changecount value is incremented in an
Expander
device only if it initiates a Broadcast(Change). So if a
Broadcast(Change)
is initiated by some Expander somewhere in same SAS Domain, the topmost
expander will just forward the Broadcast(Change). 
  In this case obviously the changecount value of topmost expander is
not
changed. Then Why this changecount value check is needed after
completing
the configuration of route table?

<SJ> All expanders ChangeCount can be checked using Report General.
For all expanders found with a updated change count, 
the initiator can look at each phy of the expander to understand what
has
changed.

2. How the routing table in all the configurable expander devices are
cleared before starting rediscover process for some reason.
   It is ok for a self configuring expander as it may handle with some
internal function. But for other configurable expander devices How the
route
table is cleared? 
  Am I missing any SMP Request function meant for this??

<SJ> The initiator should not clear the routing tables at the start of
each
rediscover.
This would disrupt current IO or SMP traffic. 
The initiator should only change what route entries that needs to be
changed

and leave all table entries that are correct as is. 
 

Any input on this will be helpful

Thanks & Regards
Subra
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