Re: [RFC] SAS domain layout for Linux sysfs

[Christoph Hellwig]

On Tue, Apr 26, 2005 at 11:18:07AM -0400, Luben Tuikov wrote:
> On 04/25/05 14:18, Christoph Hellwig wrote:
> > The point is that discovery must happen for each HBA separately because
> > we absolutely do not want to have global state.
> 
> OK.
> 
> Can you please define "global state"?

Sure, quoting your initial mail:

/----------------------------------------------------------------------
| 2. Sysfs SAS Domain
| -------------------
|
| Represent everything which "sits out there" in the SAS
| domain, irrespective of how you connect to it.
|
| /sys/bus/sas/
| /sys/bus/sas/<WWN_ta0>/
| /sys/bus/sas/<WWN_ta0>/phys/
|
| ...
\----------------------------------------------------------------------

Here you have a global hiearchy.  We are not interested in that, though -
we only care for what's visible from a certain HBA.

> In SAS, when the domain changes, the controller(s) connected to the
> domain get notification and pass it to the discovery process, which
> will run again.

Same as with fibre channel, and that's fine and expected.

> Overall, since the discovery process gets (internally) a "picture"
> of the domain out there, it would be appropriate to show this
> "picture" to the user.

Absolutely. 
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