User manual REDHAT DEVICE-MAPPER MULTIPATH 5.2 CONFIGURATION

[. . . ] Using Device-Mapper Multipath Configuration and Administration 5. 2 DM_Multipath ISBN: N/A Publication date: July 2008 Using Device-Mapper Multipath This book provides information on using the Device-Mapper Multipath feature of Red Hat Enterprise Linux 5. 2 Using Device-Mapper Multipath: Configuration and Administration Copyright © 2008 Red Hat, Inc. Copyright © 2008 Red Hat, Inc. This material may only be distributed subject to the terms and conditions set forth in the Open Publication License, V1. 0 or later with the restrictions noted below (the latest version of the OPL is presently available at http://www. opencontent. org/openpub/). Distribution of substantively modified versions of this document is prohibited without the explicit permission of the copyright holder. Distribution of the work or derivative of the work in any standard (paper) book form for commercial purposes is prohibited unless prior permission is obtained from the copyright holder. [. . . ] Setting Up DM-Multipath The local disk or disks should no longer be listed in the new multipath maps, as shown in the following example. [root@rh4cluster1 ~]# multipath -F [root@rh4cluster1 ~]# multipath -v2 create: 3600a0b80001327d80000006d43621677 [size=12 GB][features="0"][hwhandler="0"] \_ round-robin 0 \_ 2:0:0:0 sdb 8:16 \_ 3:0:0:0 sdf 8:80 create: 3600a0b80001327510000009a436215ec [size=12 GB][features="0"][hwhandler="0"] \_ round-robin 0 \_ 2:0:0:1 sdc 8:32 \_ 3:0:0:1 sdg 8:96 create: 3600a0b80001327d800000070436216b3 [size=12 GB][features="0"][hwhandler="0"] \_ round-robin 0 \_ 2:0:0:2 sdd 8:48 \_ 3:0:0:2 sdh 8:112 create: 3600a0b80001327510000009b4362163e [size=12 GB][features="0"][hwhandler="0"] \_ round-robin 0 \_ 2:0:0:3 sde 8:64 \_ 3:0:0:3 sdi 8:128 3. Adding Devices to the Multipathing Database By default, DM-Multipath includes support for the most common storage arrays that support DM-Multipath. The default configuration values, including supported devices, can be found in the multipath. conf. defaults file. If you need to add a storage device that is not supported by default as a known multipath device, edit the /etc/multipath. conf file and insert the appropriate device information. For example, to add information about the HP Open-V series the entry looks like this: devices { device { vendor "HP" product "OPEN-V. " getuid_callout "/sbin/scsi_id -g -u -p0x80 -s /block/%n" } } 14 Multipath Devices For more information on the devices section of the configuration file, see Section 5, "Configuration File Devices". 15 16 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. 7/multipath. conf. defaults file. 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. 7/multipath. conf. annotated. 1. Configuration File Overview The multipath configuration file is divided into the following sections: blacklist Listing of specific devices that will not be considered for multipath. Usually the default blacklist section is commented out. blacklist_exceptions Listing of multipath candidates that would otherwise be blacklisted according to the parameters of the blacklist section. The DM-Multipath Configuration File General default settings for DM-Multipath. multipaths Settings for the characteristics of individual multipath devices. These values overwrite what is specified in the defaults and devices sections of the configuration file. devices Settings for the individual storage controllers. These values overwrite what is specified in the defaults section of the configuration file. [. . . ] Occasionally, the path state and the dm state of a device will temporarily not agree. Note When a multipath device is being created or modified, the path group status and the dm status are not known. Also, the features are not always correct. When a multipath device is being listed, the path group priority is not known. 2. Multipath Queries with multipath Command You can use the -l and -ll options of the multipath command to display the current multipath configuration. [. . . ]