Red Hat ENTERPRISE LINUX 5.1 DM MULTIPATH Configuration And Administration Manual

Chapter 2. Multipath Devices6a cluster. For information on the multipaths section of the multipath configuration file, see seeSection 4.4, “Multipaths Device Configuration Attributes”.• If you want the system-defined user-friendly names to be consistent across all nodes in the cluster,set up all of the multipath devices on one machine. Then copy the /var/lib/multipath/bindings file from that machine to all the other machines in the cluster.2.3. Multipath Device AttributesIn addition to the user_friendly_names and alias options, a multipath device has numerousattributes. You can modify these attributes for a specific multipath device by creating an entry forthat device in the multipaths section of the multipath configuration file. For information on themultipaths section of the multipath configuration file, see see Section 4.4, “Multipaths DeviceConfiguration Attributes”.2.4. Multipath Devices in Logical VolumesAfter creating multipath devices, you can use the multipath device names just as you would use aphysical device name when creating an LVM physical volume. For example, if /dev/mapper/mpath0is the name of a multipath device, the following command will mark /dev/mapper/mpath0 as aphysical volume.pvcreate /dev/mapper/mpath0You can use the resulting LVM physical device when you create an LVM volume group just as youwould use any other LVM physical device.When you create an LVM logical volume that uses active/passive multipath arrays as the underlyingphysical devices, you should include filters in the lvm.conf to exclude the disks that underlie themultipath devices. This is because if the array automatically changes the active path to the passivepath when it receives I/O, multipath will failover and failback whenever LVM scans the passive path ifthese devices are not filtered. For active/passive arrays that require a command to make the passivepath 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 inthe devices section of the file.filter = [ "r/disk/", "r/sd.*/", "a/.*/" ]