Labeling Multipath drives

[Jeffrey O'brien]

>>> 
From: 	Kenny Lussier <klussier at gmail.com>
To:	<gnhlug-discuss at gnhlug.org>
Date: 	3/18/2009 8:49 AM
Subject: 	Labeling Multipath drives

Hi All,


I currently have a failover cluster  with a shared  iSCSI disk. It is just
an ext3 partition that has a disk label. If the primary box drops, the
backup box (through the magic of clustering), knows that it needs to mount
the disk where "LABEL=HA_DISK". However, I am soon going to be moving the
storage to a fiber channel SAN. The boxes will each have two FC HBA's in
them, giving them each eight total paths to the SAN volume. The problem that
I have is that if I use e2label on the partition that ends up in
/dev/mapper, I can't mount by label. I get an error saying "Multiple drives
found with identical label". Does anyone know how to work around this?

TIA,
Kenny

>>>

Kenny, you will need to install/configure the multipathing software.  Linux does have native mpath drivers which will create a virtual device from the mutliple devices shown so /dev/mpath/mpath0p1 would consist of /dev/sdc1, /dev/sdd1, etc...  look up "dm-multipath" for configuration setups for your environment.  The type of SAN you have too will play a role in configuration if the SAN has Active/Active or Active/Passive controllers, you may want to have an active/passive multipath configuration in the OS or an active/active setup.

If you are using EMC FC SANs, you could always pay for powerpath as long as your wallet is deep ;) 

Also in your cluster have you looked at using a clustered filesystem so both systems have an active mount so you dont have to worry about mounting?  Generally a clustered filesystem is required for clusters, GFS, OCFS2, VxFS.

Jeff