Linux Device Mapper Multipath

Device Mapper Multipath is included in the Linux operating system distributions. Device Mapper is an infrastructure in the Linux kernel. It provides a generic way to create virtual layers of block devices. It supports striping,mirroring, snapshots, concatenation, and multipathing. The multipath feature is provided with combination of DM Multipath kernel modules and multipath-tools user-space package.

How to check Disk Multipath in Linux,

Usage: multipath [-v level] [-d] [-l|-ll|-f|-F]
[-p failover|multibus|group_by_serial|group_by_prio]
[device]

Eg:-
[root@linux01:/root]# multipath -ll

mpath2 (360060e80046a310000006a3100000da9)
[size=34 GB][features="1 queue_if_no_path"][hwhandler="0"]
\_ round-robin 0 [active]
\_ 1:0:0:4 sdac 65:192 [active][ready]
\_ 0:0:0:4 sde 8:64 [active][ready]

mpath23 (360060e80046a310000006a3100000da6)
[size=34 GB][features="1 queue_if_no_path"][hwhandler="0"]
\_ round-robin 0 [active]
\_ 0:0:0:1 sdb 8:16 [active][ready]
\_ 1:0:0:1 sdz 65:144 [active][ready]

mpath1 (360060e80046a310000006a3100000da8)
[size=34 GB][features="1 queue_if_no_path"][hwhandler="0"]
\_ round-robin 0 [active]
\_ 1:0:0:3 sdab 65:176 [active][ready]
\_ 0:0:0:3 sdd 8:48 [active][ready]

mpath22 (360060e80046a310000006a3100000da5)
[size=34 GB][features="1 queue_if_no_path"][hwhandler="0"]
\_ round-robin 0 [active]
\_ 0:0:0:0 sda 8:0 [active][ready]
\_ 1:0:0:0 sdy 65:128 [active][ready]

Multipath Help file info
---------------------
Usage: multipath [-v level] [-d] [-l|-ll|-f|-F]
[-p failover|multibus|group_by_serial|group_by_prio]
[device]

-v level verbosity level

0 no output
1 print created devmap names only
2 default verbosity
3 print debug information
-b file bindings file location
-d dry run, do not create or update devmaps
-l show multipath topology (sysfs and DM info)
-ll show multipath topology (maximum info)
-f flush a multipath device map
-F flush all multipath device maps
-p policy force all maps to specified policy :
failover 1 path per priority group
multibus all paths in 1 priority group
group_by_serial 1 priority group per serial
group_by_prio 1 priority group per priority lvl
group_by_node_name 1 priority group per target node

device limit scope to the device's multipath
(udev-style $DEVNAME reference, eg /dev/sdb
or major:minor or a device map name)