2.4. Multipath Devices in Logical Volumes

After creating multipath devices, you can use the multipath device names just as you would use a physical device name when creating an LVM physical volume. For example, if /dev/mapper/mpath0 is the name of a multipath device, the following command will mark /dev/mapper/mpath0 as a physical volume.

pvcreate /dev/mapper/mpath0

pvcreate /dev/mapper/mpath0

You can use the resulting LVM physical device when you create an LVM volume group just as you would use any other LVM physical device.

When you create an LVM logical volume that uses active/passive multipath arrays as the underlying physical devices, you should include filters in the lvm.conf file to exclude the disks that underlie the multipath devices. This is because if the array automatically changes the active path to the passive path when it receives I/O, multipath will failover and failback whenever LVM scans the passive path if these devices are not filtered. For active/passive arrays that require a command to make the passive path active, LVM prints a warning message when this occurs.

To filter all SCSI devices in the multipath configuration file (lvm.conf), include the following filter in the devices section of the file.

filter = [ "r/disk/", "r/sd.*/", "a/.*/" ]

filter = [ "r/disk/", "r/sd.*/", "a/.*/" ]