In CentoS/ RHEL 5, the device mapper multipath is installed by default. In order to avoid any conflict with third party multipath software, it is advised to disable the native RHEL device-mapper-multipath software. Follow the steps below to disable the dm-multipath in RHEL 5 systems.
Disabling dm-multipath
1. To disable device-mapper-multipath, turn it off with the chkconfig command. chkconfig command makes sure that dm-multipath is not started after reboot or service restart.
# chkconfig multipathd off
2. In addition, make sure the file /etc/sysconfig/mkinitrd/multipath has the following line:
MULTIPATH=NO
The purpose of the /etc/sysconfig/mkinitrd/multipath file, is to help mkinitrd determine whether or not to include the dm-multipath modules in the initrd image file.
3. By default, /etc/multipath.conf has all devices blacklisted. If this default configuration has been changed, the change should be reverted. If the devices are not blacklisted, then running the multipath command could cause a conflict with other multipathing software. The /etc/multipath.conf file should contain the following:
# Blacklist all devices by default. Remove this to enable multipathing
# on the default devices.
blacklist {
devnode "*"
}
The above steps will ensure that device-mapper-multipath does not conflict with any other multipathing solution in use.