HP Serviceguard Extended Distance Cluster for Linux Deployment Guide, First Edition, December 2006

Configuring your Environment for Software RAID
Creating Volume Groups and Configuring VG Exclusive Activation on the MD Mirror
Chapter 3 73
Creating Volume Groups and Configuring VG
Exclusive Activation on the MD Mirror
Once you create the MD mirror device, you need to create volume groups
and logical volumes on it. Creating the volume group and logical volume
infrastructure on an MD device is similar to creating the same on a
single device. However, when you create a logical volume on an MD
device, it can be done on a physical disk (LUN) or on a partition.
For example - Let us assume that /dev/sde and /dev/sdf are two
physical disks that form the md device /dev/md0. The persistent device
names for /dev/sde and /dev/sdf are /dev/hpdev/md0_mirror0 and
/dev/hpdev/md0_mirror1 respectively. When you create a logical
volume, duplicate entries are detected for the two physical disks that
form the mirror device. As a result, the logical volume is not created and
an error message is displayed. Following is a sample of the error message
that is displayed:
Found duplicate PV 9w3TIxKZ6lFRqWUmQm9tlV5nsdUkTi4i: using
/dev/sde not /dev/sdf
With this error, you cannot create a new volume group on /dev/md0. As a
result, you must create a filter for LVM. To create a filter, add the
following line in the /etc/lvm/lvm.conf file:
filter = [ "r|/dev/cdrom|","r|/dev/hpdev/md0_mirror0|",
"r|/dev/hpdev/md0_mirror1|" ]
where /dev/hpdev/md0_mirror0 and /dev/hpdev/md0_mirror1 are the
persistent device names of the devices /dev/sde and /dev/sdf
respectively.
NOTE When adding the filter, ensure that you use the persistent names of all
the devices used in the mirrors.
This prevents these mirror devices from being scanned or used for logical
volumes. You have to reload LVM with /etc/init.d/lvm
force-reload.