Red Hat Knowledgebase

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.

This is an example of an output:

snow (1494554000000000000000000030000000300940111008000)
[size=197 MB][features="0"][hwhandler="0"]
\_ round-robin 0 [active]
 \_ 5:0:0:1 sdk 8:160 [active][ready]
\_ round-robin 0 [enabled]
 \_ 5:0:0:0 sdh 8:112 [active][ready]

The format is as follows:

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]

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 [path_status][dm_status_if_known]

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
• 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.