[PATCH v1 1/2] nvme: drop multipath config option

[Hannes Reinecke]

On 7/19/23 14:12, Daniel Wagner wrote:
> On Wed, Jul 19, 2023 at 01:38:55PM +0200, Keith Busch wrote:
>> Yeah, dm-mpath is such a setup this was intended to prevent, as well as
>> out-of-tree alternatives. Not that I advocating one way or another at
>> this point; I'm just trying to set the context for why this message
>> exists for discussing your patchset.
> 
> Fair enough.
> 
>> I'm curious why a proprietary module is even used, though. Is the
>> driver's native handling doing something undesirable, or is this to
>> cater to some vendor specific behavior outside the spec? If the former,
>> I'd like to understand the problem and see if there's something we can
>> improve.
> 
> Unfortunatly, I don't have any insides into PowerPath, or what it tries to
> achieve. I suspect it's more vendor specific handling features. I'll ask if
> there is a feature gap we could address in upstream.
> 
 From my perspective there is no feature gap. With dm-multipath there 
used to be one, as powerpath would provide /dev/sd* devices, not the 
/dev/dm-* devices from dm-multipath.
Also powerpath was/is able to detect which array is being used, and
pull all sorts of information from it.
Not that we really need that, though.

Other than that the functionality is pretty much identical.

PowerPath is primarily there as Dell/EMC used to recommend using 
PowerPath, and customer are wont to do whatever the IHV tells them.

So really, the issue not about PowerPath.

The issue is about dm-multipath, which requires this option to work at 
all. And that is a really contentious issue which I will not engage upon.

Good luck.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		           Kernel Storage Architect
hare at suse.de			                  +49 911 74053 688
SUSE Software Solutions Germany GmbH, Frankenstr. 146, 90461 Nürnberg
Managing Directors: I. Totev, A. Myers, A. McDonald, M. B. Moerman
(HRB 36809, AG Nürnberg)