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Chapter 4. The DM-Multipath Configuration File
By default, DM-Multipath provides configuration values for the most common uses of multipathing. In addition, DM-Multipath includes support for the most common storage arrays that support DM-Multipath. The default configuration values and the supported devices can be found in the
/usr/share/doc/device-mapper-multipath-0.4.5/multipath.conf.defaults file.
Note
The location and contents of the
multipath.conf.defaults file may differ slightly from the example shown in this chapter depending on the release of RHEL 4 that you are running.
You can override the default configuration values for DM-Multipath by editing the
/etc/multipath.conf configuration file. If necessary, you can also add a storage array that is not supported by default to the configuration file. This chapter provides information on parsing and modifying the multipath.conf file. It contains sections on the following topics:
- Configuration file overview
- Configuration file blacklist
- Configuration file defaults
- Configuration file multipaths
- Configuration file devices
In the multipath configuration file, you need to specify only the sections that you need for your configuration, or that you wish to change from the default values specified in the
multipath.conf.defaults file. 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.
The configuration file allows regular expression description syntax.
An annotated version of the configuration file can be found in
/usr/share/doc/device-mapper-multipathd-0.4.5/multipath.conf.annotated.
4.1. Configuration File Overview
The multipath configuration file is divided into the following sections:
- devnode_blacklist
- Listing of specific devices that will not be considered for multipath. By default all devices are blacklisted. Usually the default
devnode_blacklistsection is commented out. - defaults
- General default settings for DM-Multipath.
- multipaths
- Settings for the characteristics of individual multipath devices. These values overwrite what is specified in the
defaultsanddevicessections 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.
When the system determines the attributes of a multipath device, first it checks the multipath settings, then the per devices settings, then the multipath system defaults.
