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Re: [Linux-cluster] Multipathed quorum disk




Le 1 sept. 07 à 02:57, Claudio Tassini a écrit :

Hi,

I recently upgraded a 2-nodes cluster adding two more nodes. I would like a single node to remain in cluster even if the other three are out of service, so I'm trying to add a quorum disk to the cluster.

The problem is that the quorum disk is a LUN in a shared storage which has not the same device name through all the cluster nodes. Moreover, we use device-mapper AND lvm. I could resolve the problem using an lvm logical volume, because it would always have the same name and recognize the underlying "dm" or "sd" device name even if it changes across a reboot, but I've read that it's not advisable to use a logical volume as quorum device.

Any idea?

--
Claudio Tassini
--
Linux-cluster mailing list


using multipath -ll you'll see that your multipath device has got a unique id (wwid) :

# multipath -ll
/dev/mpath/mpath2 (200c0b60a76000032) dm-3 SNAP,FILEDISK
[size=10M][features=0][hwhandler=0]
\_ round-robin 0 [prio=0][active]
\_ 2:0:0:0 sdd 8:48  [active][ready]
\_ 1:0:0:0 sdc 8:32  [active][ready]

all you have to do then, is to modify your /etc/multipath.conf file to ask a fixed name for this multipath device instead of having it get a dynamique name (/dev/mpath/mpathx) :

/etc/multipath.conf :

...
multipaths {
        multipath {
                wwid                    200c0b60a76000032
                alias                   qdsk1
        }
}

and then :

# multipath -ll
[root titan2 ~]# multipath -ll
qdsk1 (200c0b60a76000032) dm-4 SNAP,FILEDISK
[size=10M][features=0][hwhandler=0]
\_ round-robin 0 [prio=0][active]
\_ 4:0:0:0 sdf 8:80  [active][ready]
\_ 3:0:0:0 sde 8:64  [active][ready]

(please, be warn that the first time you do it, it rename the multipath device to the name you have ask for, but it fails to rename the /dev/mpath/ device, so you have to do it manually once).

do it on all your cluster members and they all get the multipath device with the same name.

I have also encoutered a problem with cman that refuse to register a node with more than 16 chars (qdiskd register the qdisk device as a node name). So you must ensure your device path is less than 16 chars for a qdisk device (this is why I use /dev/mpath/qdsk1 instead of /dev/mpath/qdisk1).

Regards,

-- 

Alain RICHARD <mailto:alain richard equation fr>

EQUATION SA <http://www.equation.fr/>

Tel : +33 477 79 48 00     Fax : +33 477 79 48 01

E-Liance, Opérateur des entreprises et collectivités,

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