How do SAS self-configuring expanders self configure?

Elliott, Robert (Server Storage) Elliott at hp.com
Thu Jan 26 16:21:42 PST 2006


* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert (Server Storage)" <Elliott at hp.com>
*
A self-configuring expander is one that fills in its routing tables on
its own, and does not expose them through REPORT/CONFIGURE ROUTING
INFORMATION functions.

4.1.5 describes the two types:
"Expander devices with expander phys with the table routing attribute
contain an expander route table. The expander route table may be
configurable. An expander device with a configurable route table
depends on a management application client within the SAS domain 
to use the discover process (see 4.7) to configure the expander 
route table.

An expander device with expander phys with the table routing
attribute that does not have a configurable route table shall be 
self-configuring, and shall contain a management application client
and SMP initiator port to perform the discover process to configure 
its own expander route table."

What more does the standard need to say?  

The details of the route table implementation are vendor-specific.
The addresses it must add (in whatever manner) are defined by 
the discover process.

One detail lacking is a way for self-configuring expanders to
report their status with regard to error handling.  We agreed 
to deal with that in SAS-2.

We briefly discussed adding a generation count to all the
SMP functions so a management app client would realize that
configuration started changing since it last checked the
REPORT GENERAL function CONFIGURING bit, but decided the
BROADCAST (CHANGE) when configuration stops was adequate
(it retriggers a new discover process by that app client,
which will pick up a consistent new set of results).

More than one vendor has implemented self-configuration in
a real expander, and I haven't heard any complaints about not
understanding what to do.

--
Rob Elliott, elliott at hp.com
Hewlett-Packard Industry Standard Server Storage Advanced Technology
https://ecardfile.com/id/RobElliott


 

> -----Original Message-----
> From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf 
> Of Ralph Weber
> Sent: Thursday, January 26, 2006 4:10 PM
> To: T10, Reflector
> Subject: How do SAS self-configuring expanders self configure?
> 
> * From the T10 Reflector (t10 at t10.org), posted by:
> * Ralph Weber <roweber at ieee.org>
> *
> I have been told several times that SAS-1.1 (and by inference SAS-2)
> define how self configuring expanders do their self configuration
> thing. I have taken a stab at finding this definition:
> 
>   http://www.t10.org/ftp/t10/document.06/06-087r0.pdf
> 
> The only 'self-configuring expander devices shall ...' I can find
> in SAS-2 (give or take a few words) is:
> 
>   Self-configuring expander devices shall originate a BROADCAST
>   (CHANGE) when they are done configuring.
> 
> Anyone with greater insight than I, is welcome to engrave the SAS-2
> clause number for the location of these mythical self configuration
> requirements on a 4x4 and beat me about the head and 
> shoulders with it.
> 
> On the other hand, the next person who claims that SAS-x defines how
> self configuring expanders work is advised to arrive with such a 4x4
> in their hip pocket in order to have any hope of being taken 
> seriously.
> 
> All the best,
> 
> .Ralph
> 
> 
> *
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