Re: Getting device-mapper failure notifications

[Mike Snitzer <snitzer@redhat.com>]

On Wed, Feb 24 2016 at  5:25am -0500,
Hannes Reinecke <hare@suse.de> wrote:

> On 02/24/2016 01:00 PM, Andy Grover wrote:
> > On 02/01/2016 11:07 PM, Avishay Traeger wrote:
> >> Hi all,
> >> I have a system where various configurations are possible - iSCSI/FC,
> >> single paths and multiple.  For multiple I of course use device-mapper.
> >> I was wondering if it was possible to:
> >> 1. use it for cases where I have a single path.
> >> 2. create a monitoring process that can take some action (e.g., send a
> >> notification via message queue) in the case of some failure that would
> >> normally cause failover.
> > 
> > Does dm-multipath support a single path? I don't know...
> > 
> Pshaw.
> Of course it does.
> 
> (Might be that RH has some magic disallowing that, but certainly there's
> nothing in the source which forbids it. In fact I recommend it when
> using iSCSI)

No, RH provided dm-multipath doesn't disallow single path multipath.
Not sure why you engage in raising such doubt -- red hat follows
upstream.  period.

multipathd can be configured to look for multiple paths
('find_multipaths yes' in multipath.conf) but there is nothing in the
kernel disallowing the use of dm-multipath with a single path.