[Linux-cluster] Persistent naming with UDEV and EMC's Powerpath

[Roberto Fratelli]

Hello everyone !

I'm trying to set up a quorum disk in a 2-node redhat cluster (RHEL 4.7). Both nodes are attached to a SAN Clariion over qlogic HBA's and i'm using EMC's powerpath.

The problem i'm facing is that the disks's device names are different across the nodes. For example, the lun i elected to be my quorum disk is called '/dev/emcpowerf' at node-a and '/dev/emcpowerd' at node-b, so i can't use the device name (/dev/emcpowerXX) in my cluster.conf file. In a attempt to overcome this i've tried to use the disk label instead :

<quorumd label="97196ef0-da2f-4b79-a5c5-999dce70d677" interval="2" tko="10" votes="1"/>

But did not work also, because this way it finds '/dev/sdXX' before '/dev/emcpowerXX':

root at node-a:~ # cman_tool nodes
Node  Votes Exp Sts  Name
   0    1    0   M   /dev/sdf1
   1    1    2   M   node-a
   2    1    2   M   node-b
root at node-a:~ #


Since this '/dev/sdf' is just one of the paths i have under powerpath (it has 4 paths per HBA, 8 paths per lun total) i can't keep it this way because in a event of lun trespass (clariion does it very often) i would loose quorum. My understanding is that i need some kind of "persistent binding" so i can use Powerpath's pseudo-device '/dev/emcpowerXX', so i tried to create a UDEV rule like this:

[root at node-a RSM]# cat 75-quorum.rules
KERNEL=="emcpower[a-z]1, SYSFS{label}=="97196ef0-da2f-4b79-a5c5-999dce70d677", SYMLINK+="discodequorum%n"
[root at node-a RSM]#


Which did not worked, i think because UDEV starts way before powerpath. Does anyone here faced this problem before ? how can i keep the device names persistent across the nodes (at least for the quorum disk) ?


Below some more info on my quorum's disk:


root at node-a:~ # mkqdisk -L
mkqdisk v0.5.2
/dev/sdf1:
        Magic:                eb7a62c2
        Label:                97196ef0-da2f-4b79-a5c5-999dce70d677
        Created:              Mon Dec 24 11:47:11 2007
        Host:                 node-a
        Kernel Sector Size:   512

/dev/sdo1:
        Magic:                eb7a62c2
        Label:                97196ef0-da2f-4b79-a5c5-999dce70d677
        Created:              Mon Dec 24 11:47:11 2007
        Host:                 node-a
        Kernel Sector Size:   512

/dev/sdx1:
        Magic:                eb7a62c2
        Label:                97196ef0-da2f-4b79-a5c5-999dce70d677
        Created:              Mon Dec 24 11:47:11 2007
        Host:                 node-a
        Kernel Sector Size:   512

/dev/sdag1:
        Magic:                eb7a62c2
        Label:                97196ef0-da2f-4b79-a5c5-999dce70d677
        Created:              Mon Dec 24 11:47:11 2007
        Host:                 node-a
        Kernel Sector Size:   512

/dev/sdap1:
        Magic:                eb7a62c2
        Label:                97196ef0-da2f-4b79-a5c5-999dce70d677
        Created:              Mon Dec 24 11:47:11 2007
        Host:                 node-a
        Kernel Sector Size:   512

/dev/sday1:
        Magic:                eb7a62c2
        Label:                97196ef0-da2f-4b79-a5c5-999dce70d677
        Created:              Mon Dec 24 11:47:11 2007
        Host:                 node-a
        Kernel Sector Size:   512

/dev/sdbh1:
        Magic:                eb7a62c2
        Label:                97196ef0-da2f-4b79-a5c5-999dce70d677
        Created:              Mon Dec 24 11:47:11 2007
        Host:                 node-a
        Kernel Sector Size:   512

/dev/sdbq1:
        Magic:                eb7a62c2
        Label:                97196ef0-da2f-4b79-a5c5-999dce70d677
        Created:              Mon Dec 24 11:47:11 2007
        Host:                 node-a
        Kernel Sector Size:   512

/dev/emcpowerf1:
        Magic:                eb7a62c2
        Label:                97196ef0-da2f-4b79-a5c5-999dce70d677
        Created:              Mon Dec 24 11:47:11 2007
        Host:                 node-a
        Kernel Sector Size:   512

root at node-a:~ #



[root at node-b ~]# mkqdisk -L
mkqdisk v0.5.2
/dev/sdf1:
        Magic:                eb7a62c2
        Label:                97196ef0-da2f-4b79-a5c5-999dce70d677
        Created:              Mon Dec 24 11:47:11 2007
        Host:                 node-a
        Kernel Sector Size:   512

/dev/sdo1:
        Magic:                eb7a62c2
        Label:                97196ef0-da2f-4b79-a5c5-999dce70d677
        Created:              Mon Dec 24 11:47:11 2007
        Host:                 node-a
        Kernel Sector Size:   512

/dev/sdx1:
        Magic:                eb7a62c2
        Label:                97196ef0-da2f-4b79-a5c5-999dce70d677
        Created:              Mon Dec 24 11:47:11 2007
        Host:                 node-a
        Kernel Sector Size:   512

/dev/sdag1:
        Magic:                eb7a62c2
        Label:                97196ef0-da2f-4b79-a5c5-999dce70d677
        Created:              Mon Dec 24 11:47:11 2007
        Host:                 node-a
        Kernel Sector Size:   512

/dev/sdap1:
        Magic:                eb7a62c2
        Label:                97196ef0-da2f-4b79-a5c5-999dce70d677
        Created:              Mon Dec 24 11:47:11 2007
        Host:                 node-a
        Kernel Sector Size:   512

/dev/sday1:
        Magic:                eb7a62c2
        Label:                97196ef0-da2f-4b79-a5c5-999dce70d677
        Created:              Mon Dec 24 11:47:11 2007
        Host:                 node-a
        Kernel Sector Size:   512

/dev/sdbh1:
        Magic:                eb7a62c2
        Label:                97196ef0-da2f-4b79-a5c5-999dce70d677
        Created:              Mon Dec 24 11:47:11 2007
        Host:                 node-a
        Kernel Sector Size:   512

/dev/sdbq1:
        Magic:                eb7a62c2
        Label:                97196ef0-da2f-4b79-a5c5-999dce70d677
        Created:              Mon Dec 24 11:47:11 2007
        Host:                 node-a
        Kernel Sector Size:   512

/dev/emcpowerd1:
        Magic:                eb7a62c2
        Label:                97196ef0-da2f-4b79-a5c5-999dce70d677
        Created:              Mon Dec 24 11:47:11 2007
        Host:                 node-a
        Kernel Sector Size:   512

[root at node-b ~]#