Multipath Device Attributes; Multipath Devices In Logical Volumes - Red Hat CLUSTER SUITE 4.7 DM MULTIPATH Configuration And Administration Manual

Chapter 2. Multipath Devices
a cluster. For information on the multipaths section of the multipath configuration file, see see
Section 4.4, "Multipaths Device Configuration
• 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 bindings file from that machine
to all the other machines in the cluster. The bindings file is located at /var/lib/multipath/
bindings by default, but you can set this value to a different location with the bindings_file
parameter of the defaults section of the configuration file.

2.3. Multipath Device Attributes

In addition to the user_friendly_names and alias options, a multipath device has numerous
attributes. You can modify these attributes for a specific multipath device by creating an entry for
that device in the multipaths section of the multipath configuration file. For information on the
multipaths section of the multipath configuration file, see see
Configuration Attributes".

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
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/.*/" ]
6
Attributes".
Section 4.4, "Multipaths Device