Brief - multipath Command

Use the Linux multipath command to configure and manage multipathed devices.

General syntax for the multipath command:

multipath [-v verbosity] [-d] [-h|-l|-ll|-f|-F] [-p failover|multibus|group_by_serial|group_by_prio|group_by_node_name] 

Configure multipath devices

#multipath

Configure a specific multipath device

#multipath devicename

Replace devicename

 Replace devicename with the device node name such as /dev/sdb (as shown by udev in the $DEVNAME variable), or in the major:minor format.Selectively suppress a multipath map, and its device-mapped partitions:
#multipath -f

Display potential multipath devices

Display potential multipath devices, but do not create any devices and do not update device maps (dry run):
#multipath -d

Configure multipath devices and display multipath map information

#multipath -v2  
#multipath -v3

The -v2 option in multipath -v2 -d shows only local disks. Use the -v3 option to show the full path list.lliiFor example

#multipath -v3 -d

Display the status of all multipath devices, or a specified multipath device

#multipath -ll 
#multipath -ll 

Flush all unused multipath device maps 

Flush all unused multipath device maps (unresolves the multiple paths; it does not delete the device)

#multipath -F
#multipath -F  

Set the group policy

multipath -p [failover|multibus|group_by_serial|group_by_prio|group_by_node_name] 
Group Policy Options for the multipath -p Command

Policy Option             Description
failover                        One path per priority group. You can use only one path at a time.
multibus                       All paths in one priority group.
group_by_serial           One priority group per detected SCSI serial number 
group_by_prio              One priority group per path priority value. Paths with the same priority                          are in the same priority group. Priorities are determined by callout                                           programs specified as a global, per-controller, or per-multipath                                               option in  the /etc/multipath.conf configuration file.
group_by_node_          
name                           One priority group per target node name. Target node names are                                            fetched in the /sys/class/fc_transport/target*/node_name location.