[linux-lvm] Discussion: performance issue on event activation mode

[Martin Wilck]

On Di, 2021-06-08 at 10:39 -0500, David Teigland wrote:
> 
> . Use both native md/mpath detection *and* udev info when it's
> readily
>   available (don't wait for it), instead of limiting ourselves to one
>   source of info.  If either source indicates an md/mpath component,
>   then we consider it true.

Hm. You can boot with "multipath=off" which udev would take into
account. What would you do in that case? Native mpath detection would
probably not figure it out.

multipath-tools itself follows the "try udev and fall back to native if
it fails" approach, which isn't always perfect, either.

> A third related improvement that could follow is to add stronger
> native
> mpath detection, in which lvm uses uses /etc/multipath/wwids,
> directly or
> through a multipath library, to identify mpath components.  This
> would
> supplement the existing sysfs and udev sources, and address the
> difficult
> case where the mpath device is not yet set up.
> 

Please don't. Use libmpathvalid if you want to improve in this area.
That's what it was made for.

Regards,
Martin