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



Hi Roberto.

	 You can use the emcpadm() command to rename the device on each
node so they are all the same. The syntax is "emcpadm rename[pseudo] -s
src pseudodevice -t tgt pseudodevice". For example, if on node A the
device is emcpowerg and you wish it to be be emcpowerq you would issue:

# emcpadm rename -s emcpowerg -t emcpowerq 

	For each node run the "powermt display dev=all" and review the
Logical device ID that is displayed for each LUN on each node. Find your
quorom disk on each - for example, Logical device
ID=6006016018C80800B5069570B8A9D911

# powermt display dev=emcpowerg

Pseudo name=emcpowerg
CLARiiON ID=WRE00100100415
Logical device ID=6006016018C80800B5069570B8A9D911
state=alive; policy=CLAROpt; priority=0; queued-IOs=0
Owner: default=SP A, current=SP A
======================================================================
------------ Host ----------- - Stor - -- I/O Path - -- Stats ---
### HW Path I/O Paths Interf. Mode State Q-IOs Errors
======================================================================
3 lpfc sdaa SP A0 active alive 0 0
2 lpfc sdj SP A1 active alive 0 0

Then rename it....

# emcpadm rename -s emcpowerg -t emcpowerq 

...and your in business.

Regards,
Wayne.

-----Original Message-----
From: linux-cluster-bounces redhat com
[mailto:linux-cluster-bounces redhat com] On Behalf Of Roberto Fratelli
Sent: Monday, April 27, 2009 9:18 AM
To: linux-cluster redhat com
Subject: [Linux-cluster] Persistent naming with UDEV and EMC's Powerpath


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



[root 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 node-b ~]#


      

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