[Linux-cluster] Get qdisk to use /dev/mapper/mpathx devices insteadof /dev/dm-x

Celso K. Webber celsowebber at yahoo.com
Thu May 6 04:01:42 UTC 2010


Or you can map a specific LUN device ID number with a specific name under /etc/multipath.conf, so you'll always have the same device name for a specific LUN designated for the quorum device.


Regards, Celso



----- Original Message ----
From: Kit Gerrits <kitgerrits at gmail.com>
To: linux clustering <linux-cluster at redhat.com>
Sent: Wed, May 5, 2010 9:01:57 PM
Subject: Re: [Linux-cluster] Get qdisk to use /dev/mapper/mpathx devices insteadof /dev/dm-x


The danger in using /dev/dm-x is that there is no guarantee that the same
device will show up at the same place after a reboot.
Seeing as you use disklabels, this becomes a non-issue.

Aside from that, I am not aware of any other reasons not to use /dev/dm-x

-----Original Message-----
From: linux-cluster-bounces at redhat.com
[mailto:linux-cluster-bounces at redhat.com] On Behalf Of Don Hoover
Sent: woensdag 5 mei 2010 20:03
To: linux-cluster at redhat.com
Subject: [Linux-cluster] Get qdisk to use /dev/mapper/mpathx devices
insteadof /dev/dm-x

I have recently learned that its dangerous to use /dev/dm-x devices for LVM
because they do not function correctly with multipath, and that you should
always use the /dev/mapper/mpathx devices.  Something about the fact that
udev actually destroys and recreates the dm devices when paths change.

But, qdisk seems to prefer using dm-x devices.  Is there a way to get it to
prefer using /dev/mapper/mpathx devices if they are available?

I know you can spec the device instead of the label, but I would like to
avoid that.



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