Installation guide

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. T hen copy the bindings file from that machine
to all the other machines in the cluster. T he bindings file is located at
/var/lib/multipath/bindings by default, but as of RHEL 4.6 and later 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 m ultipaths section of the multipath configuration file. For information on the
m ultipaths section of the multipath configuration file, see see Section 4.4, “Multipaths Device
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/m path0 is
the name of a multipath device, the following command will mark /dev/m apper/m path0 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/.*/" ]
Chapter 2. Multipath D evices
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