The multipath
-ll command shows the current multipath topology, this includes
information regarding which path is active, how the paths are grouped, and how
the meta-devices will behave in case of a complete path loss
Sample Output is given below
-----------------------------------------------------------------------------------------------------------------------
diskname
(360014380056efd060000d00000510000) dm-3 Vendor,StorageModel
[size=1.0G][features=1
queue_if_no_path][hwhandler=0][rw]
\_ round-robin 0 [prio=100][active]
\_ 0:0:0:1 sda 8:0 [active][ready]
\_ 1:0:1:1 sdd 8:48 [active][ready]
\_ round-robin 0 [prio=20][enabled]
\_ 0:0:1:1 sdb 8:16 [active][ready]
\_ 1:0:0:1 sdc 8:32 [active][ready]
-----------------------------------------------------------------------------------------------------------------------
Each multipath device is defined using the following format:
-----------------------------------------------------------------------------------------------------------------------
action_if_any: alias (wwid_if_different_from_alias)
[size][features][hardware_handler]
-------------------------------------------------------------------------------
Where:
- action_if_any:
If multipath is performing an action, while running the command this
action will be displayed here. An action can be "reload",
"create" or "switchpg"
- alias:
is the name of the multipath device as can be found under /dev/mapper/
- wwid_if_different_from_alias: is the scsi wwid, the unique identifier of the LUN
- size:
is the size of the multipath devices
- features:
is a list of all the options enabled for this multipath device (e.g.
queue_if_no_path)
- hardware_handler:
This is 0 if no hardware handler is in use. This is 1 and the name of the
hardware handler kernel module in use.
For each path group:
----------------------------------------------------------------------------------------------------------------------
\_ scheduling_policy
[path_group_priority_if_known] [path_group_status_if_known]
-------------------------------------------------------------------------------
for example:
----------------------------------------------------------------------------------------------------------------------
\_ round-robin 0 [prio=100][active]
-------------------------------------------------------------------------------
Where:
- scheduling_policy:
is the path selector algorithm in use for this path group
- path_group_priority_if_known: Each path can have a priority assigned to it by a
callout program. Path priorities can be used to group paths by priority
and change their relative weights for the algorithm that defines the
scheduling policy.
- path_group_status_if_known: The status of the path can be one of the following:
- active - Path group currently receiving I/O requests.
- enabled - Path groups to try if the active path group
has no paths in the ready state.
- disabled - Path groups to try if the active path group
and all enabled path groups have no paths in the active state.
For each path:
---------------------------------------------------------------------------------------------------------------------------
\_ host:channel:id:lun devnode major:minor
[dm_status_if_known] [path_status]
----------------------------------------------------------------------------------
for example:
---------------------------------------------------------------------------------------------------------------------------
\_ 5:0:0:1 sdk 8:160 [active][ready]
----------------------------------------------------------------------------------
Where:
- host:channel:id:lun:
are the SCSI host, channel, id and lun values that identify the LUN
- devnode:
is the name of the device
- major:minor:
the major and minor number of the block device
- dm_status_if_known:
Is similiar to the path status, but from the kernel's point of view.
The dm status has two states: "failed", which is analogous
to "faulty", and "active" which covers all other path
states.
- path_status:
the status of the path can be one of the following:
- ready - Path is able to handle I/O requests.
- shaky - Path is up, but temporarily not available for
normal operations.
- faulty - Path is unable to handle I/O requests.
- ghost - Path is a passive path, on an active/passive
controller.
- dm_status_if_known:
Is similiar to the path status, but from the kernel's point of view. The
dm status has two states:
- failed - which is analogous to "faulty", and
- active - which covers all other path states.
