Red Hat Summit4장. Modifying the DM Multipath configuration file
Override DM Multipath default configuration values by editing the /etc/multipath.conf file to customize multipathing behavior and add support for unsupported storage arrays.
In the multipath configuration file, you need to specify only the sections that you need for your configuration, or that you need to change from the default values. If there are sections of the file that are not relevant to your environment or for which you do not need to override the default values, you can leave them commented out, as they are in the initial file.
In the configuration file, you can also use the regular expression.
If you run multipath from the initramfs file system and you make any changes to the multipath configuration files, you must rebuild the initramfs file system for the changes to take effect.
4.1. Configuration file overview
The multipath configuration file contains distinct sections for blacklists, defaults, devices, multipaths, and overrides, evaluated in priority order to determine device behavior.
The multipath configuration file is divided into the following sections:
- blacklist
- Listing of specific devices that will not be considered for multipath.
- blacklist_exceptions
-
Listing of multipath devices that would otherwise be ignored according to the parameters of the
blacklistsection. - defaults
- General default settings for DM Multipath.
- multipaths
-
Settings for the characteristics of individual multipath devices. These values overwrite what is specified in the
overrides,devices, anddefaultssections of the configuration file. - devices
-
Settings for the individual storage controllers. These values overwrite what is specified in the
defaultssection of the configuration file. If you are using a storage array that is not supported by default, you may need to create adevicessubsection for your array. - overrides
-
Settings that are applied to all devices. These values overwrite what is specified in the
devicesanddefaultssections of the configuration file.
When the system determines the attributes of a multipath device, it checks the settings of the separate sections from the multipath.conf file in the following order:
-
multipathssection -
overridessection -
devicessection -
defaultssection
The following are the ways to view the default configurations:
If you install your machine on a multipath device, the default multipath configuration applies automatically. The default configuration includes the following:
-
For a complete list of the default configuration values, execute either
multipath -tormultipathd show configcommand. -
For a list of configuration options with descriptions, see the
multipath.confman page on your system.
-
For a complete list of the default configuration values, execute either
-
If you did not set up multipathing during installation, execute the
mpathconf --enablecommand to get the default configuration.
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