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DM-Multipath in RHEL6

Components	Description
dm-multipath kernel module	Reroutes I/O and supports failover for paths and path groups.
mpathconf utility	Configures and enables device mapper multipathing.
multipath command	Lists and configures multipath devices. Normally started up with /etc/rc.sysinit, it can also be started up by a udev program whenever a block device is added or it can be run by the initramfs file system.
multipathd daemon	Monitors paths; as paths fail and come back, it may initiate path group switches. Provides for interactive changes to multipath devices. This must be restarted for any changes to the /etc/multipath.conf file.
kpartx command	Creates device mapper devices for the partitions on a device It is necessary to use this command for DOS-based partitions with DM-MP. The kpartx is provided in its own package, but the device-mapper-multipath package depends on it.

The basic procedure for configuring your system with DM-Multipath is as follows:

Install the device-mapper-multipath rpm.
Create the configuration file and enable multipathing with the mpathconf command. You can also start the multipath daemon with this command if you do not need to edit the configuration file.
If necessary, edit the multipath.conf configuration file to modify default values and save the updated file.
Start the multipath daemon.