Re: dm-multipath: Accept failed paths for multipath maps

[Mike Snitzer <snitzer@redhat.com>]

On Wed, Dec 18 2013 at  2:52am -0500,
Hannes Reinecke <hare@suse.de> wrote:

> The multipath kernel module is rejecting any map with an invalid
> device. However, as the multipathd is processing the events serially
> it will try to push a map with invalid devices if more than one
> device failed at the same time.
> So we can as well accept those maps and make sure to mark the
> paths as down.

Why is it so desirable to do this?  Reduced latency to restore at least
one valid path when a bunch of paths go down?

Why can't we just rely on userspace eventually figuring out which paths
are failed and pushing a valid map down?

Are there favorable reports that this new behavior actually helps?
Please quantify how.

(As an aside, really not a fan of parse_path doing what you've
suggested.. will look closer once I have more justification to do so)