Re: multipathd removing DM devices that don't belong to it

[Hannes Reinecke <hare@suse.de>]

On 07/24/2015 07:53 PM, Artem Danielov wrote:
> Hi,
> 
> Any chance you guys have looked into this problem? Thank you!
> 
>  
> 
> *From:* Artem Danielov
> *Sent:* Tuesday, June 16, 2015 15:02
> *To:* 'dm-devel@redhat.com'
> *Subject:* multipathd removing DM devices that don't belong to it
> 
>  
> 
> Hello,
> 
> Looking for an advice on whether this is an expected behavior or a bug.
> 
> device-mapper-multipath-0.4.9-77.el7.x86_64
> 
>  
> 
> When multipathd service starts it will remove any DM devices with
> multipath target, _even if the underlying devices are blacklisted_.
> 
> We are trying to use dmsetup directly  to implement custom multipath
> management logic separate from multipathd. But unfortunately if
> multipathd is present and enabled it removes DM devices with
> multipath target that we create.
> 
Well, hardly surprising.
ATM multipathd expects to be the only one creating multipath tables,
so of course it would try to 'rectify' the situation.

What one could try is to use a different UUID prefix (ie something
else than 'mpath') and then teach multipath to ignore all
device-mapper devices of type 'multipath' but without the 'mpath'
UUID prefix.

>  
> 
> Is this a bug?
> 
Not as such.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		               zSeries & Storage
hare@suse.de			               +49 911 74053 688
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