[dm-devel] [PATCH] multipathd: handle fpin events

[Erwin van Londen]

Hello Martin, Muneendra.

As I kicked this discussion off in the beginning of the year and seeing
the Muneendra and the broadcom people have come up with the first
iteration I can only applaud the efforts. On behalf of all storage and
linux administrators I would say "Thank you".

As for your remark Martin my view would be to try and create a modular
approach where the transport layer drivers can hook into and inform
multipathd of any event. The module in multipathd would then decide
based on configured characteristics what the actions should be. (Take
it offline, suspend for X amount of time, introduce X us delay etc...)
That way when more transport methods are used these can then
dynamically be linked into the configuration without having any impact
on other parts of the transport stack. I can imagine that Infiniband.
ethernet, SAS and others utilise different transport characteristics
and as such may need to inform the attached hosts of one or more
events. On FC this is FPIN but a similar module may be written for
other transports.

Thanks
Erwin

On Mon, 2021-12-06 at 13:58 +0000, Martin Wilck wrote:
> On Fri, 2021-12-03 at 18:02 +0100, Martin Wilck wrote:
> > 
> > 
> > Rather than adding a new config option, I'd prefer to add a new
> > value
> > "fpin" to the marginal_pathgroups option. That would make it more
> > clear
> > that the two are actually related / exclusive.
> 
> Another thought that occurred to me over the weekend: FPIN is fibre-
> channel only. What if someone has a mix of FC and other transports?
> Would it make sense to use FPIN for FC paths and "traditional"
> marginal
> path detection for others? If yes, we'd need to change the logic and
> we'd probably have to add a 4th mode ("fpin-mixed" or whatever).
> 
> Regards
> Martin
> 
> 
> 
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