Setting Up Dm-Multipath - Red Hat ENTERPRISE LINUX 5 DM MULTIPATH Configuration And Administration Manual

Chapter 3.

Setting Up DM-Multipath

This chapter provides step-by-step example procedures for configuring DM-Multipath. It includes the
following procedures:
• Basic DM-Multipath setup
• Ignoring local disks
• Adding more devices to the configuration file
3.1. Setting Up DM-Multipath
Before setting up DM-Multipath on your system, ensure that your system has been updated and
includes the device-mapper-multipath package.
Use the following procedure to set up DM-Multipath for a basic failover configuration.
1. Edit the /etc/multipath.conf file by commenting out the following lines at the top of the file.
This section of the configuration file, in its initial state, blacklists all devices. You must comment it
out to enable multipathing.
blacklist {
devnode "*"
}
After commenting out those lines, this section appears as follows.
# blacklist {
# devnode "*"
# }
2. The default settings for DM-Multipath are compiled in to the system and do not need to be
explicitly set in the /etc/multipath.conf file.
The default value of path_grouping_policy is set to failover, so in this example you do not
need to change the default value. For information on changing the values in the configuration file
to something other than the defaults, see
The initial defaults section of the configuration file configures your system that the names of the
multipath devices are of the form mpathn; without this setting, the names of the multipath devices
would be aliased to the WWID of the device.
3. Save the configuration file and exit the editor.
4. Execute the following commands:
modprobe dm-multipath
Chapter 4, The DM-Multipath Configuration File.
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