Chapter 9. Troubleshooting DM Multipath
Chapter 9. Troubleshooting DM Multipath If you have trouble implementing a multipath configuration, there are a variety of issues you can check for. The following issues may result in a slow or non-functioning multipath configuration: The multipath daemon is not running If you find you have trouble implementing a multipath configuration, ensure that the multipathd daemon is running, as described in Configuring DM Multipath . The multipathd daemon must be running to use multipathed devices. Issues with queue_if_no_path feature If a multipath device is configured with the features "1 queue_if_no_path" option, then any process that issues I/O hangs until one or more paths are restored. 9.1. Troubleshooting issues with queue_if_no_path feature If a multipath device is configured with the features "1 queue_if_no_path" option, then any process that issues I/O hangs until one or more paths are restored. To avoid this, set the no_path_retry N parameter in the /etc/multipath.conf file, where N is the number of times the system should retry a path. To use the features "1 queue_if_no_path" option without the described problem, you can disable the queueing policy at runtime for a particular LUN, for which all paths are unavailable. Procedure Disable queueing: For a specific device: For all devices: After you disable queueing, it will remain disabled until you restart or reload multipathd . Reset queueing to a value: For a specific device: For all devices: 9.2. Troubleshooting with the multipathd interactive console The multipathd -k command is an interactive interface to the multipathd daemon. Entering this command brings up an interactive multipath console. After executing this command, you can enter help to get a list of available commands and Ctrl + D to quit. Use the multipathd interactive console to troubleshoot problems you might have with your system. Procedure Display the multipath configuration, including the default values, before exiting the console: Ensure that multipath picked up all changes to the multipath.conf file: Ensure that the path checker is working properly: You can also run a single multipathd interactive command directly from the command line, without starting the interactive console. For example, to check that multipath picks up all changes to the multipath.conf file, run the following command:
multipathd disablequeueing map device multipathd disablequeueing maps multipathd restorequeueing map device multipathd restorequeueing maps multipathd -k multipathd> show config multipathd> Ctrl + D multipathd -k multipathd> reconfigure multipathd> Ctrl + D multipathd -k multipathd> show paths multipathd> Ctrl + D multipathd reconfigure