Red Hat LINUX VIRTUAL SERVER 4.7 - ADMINISTRATION Przewodnik Instalacji Pobierz pdf (Strona 33)

Chapter 5. DM-Multipath Administration and Troubleshooting

This chapter will provide information on administering DM-Multipath on a running system. It includes

sections on the following topics:

Multipath Command Output

Multipath Queries with multipath Command

Multipath Command Options

Multipath Queries with dmsetup Command

Troubleshooting with the multipathd Interactive Console

Resizing an Online Multipathed Device

5.1. Multipath Command Output

When you create, modify, or list a multipath device, you get a printout of the current device setup. T he

format is as follows.

For each multipath device:

action_if_any: alias (wwid_if_different_from_alias)

[size][features][hardware_handler]

For each path group:

\_ scheduling_policy [path_group_priority_if_known]

[path_group_status_if_known]

For each path:

\_ host:channel:id:lun devnode major:minor [path_status] [dm_status_if_known]

For example, the output of a multipath command might appear as follows:

mpath1 (3600d0230003228bc000339414edb8101) [size=10

GB][features="0"][hwhandler="0"]

\_ round-robin 0 [prio=1][active]

\_ 2:0:0:6 sdb 8:16 [active][ready]

\_ round-robin 0 [prio=1][enabled]

\_ 3:0:0:6 sdc 8:64 [active][ready]

If the path is up and ready for I/O, the status of the path is ready or active. If the path is down, the

status is faulty or failed. The path status is updated periodically by the m ultipathd daemon

based on the polling interval defined in the /etc/multipath.conf file.

The dm status is similar 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.

Occasionally, the path state and the dm state of a device will temporarily not agree.

Red Hat Enterprise Linux 4 DM Multipath

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