The in.mpathd daemon uses the settings in the /etc/default/mpathd configuration file to invoke multipathing. Changes to this file are read by in.mpathd at startup and on SIGHUP. This file contains the following default settings and information:
# # Time taken by mpathd to detect a NIC failure in ms. The minimum time # that can be specified is 100 ms. # FAILURE_DETECTION_TIME=10000 # # Failback is enabled by default. To disable failback turn off this option # FAILBACK=yes # # By default only interfaces configured as part of multipathing groups # are tracked. Turn off this option to track all network interfaces # on the system # TRACK_INTERFACES_ONLY_WITH_GROUPS=yes
How to Configure the Multipathing Configuration File shows the steps that you perform to configure the /etc/default/mpathd configuration file.
You can set a lower value of failure detection time. Sometimes, these values might not be achieved if the load on the network is too high. Then in.mpathd prints a message on the console. The message indicates that the time cannot be met. The daemon also prints the time that the daemon can meet currently. If the response comes back correctly, in.mpathd meets the failure detection time that is provided in this file.
After a failover, failback occurs when the failed interface is repaired. However, in.mpathd does not fail back the interface if FAILBACK is set to no.
As noted in Detecting Physical Interface Failures, automatic failback is supported for physical interfaces that are not present at system boot. See How to Recover a Physical Interface That Was Not Present at System Boot.
By turning off this option, in.mpathd tracks all interfaces in the system. When a failure is detected, an appropriate message is logged on the console. For this option to function properly, Ethernet addresses on all the interfaces must be unique.