Novell LINUX ENTERPRISE SERVER 10 - STORAGE ADMINISTRATION GUIDE 7-2007 Administration Manual

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Novell LINUX ENTERPRISE SERVER 10 - STORAGE ADMINISTRATION GUIDE 7-2007 Administration Manual Manual pdf 50 page image

50 SLES 10 Storage Administration Guidenovdocx (en) 6 April 20075.7 Adding Support for the Storage Subsystemto /etc/multipath.confIf you are using a storage subsystem that is automatically detected (see “Supported StorageSubsystems” on page 46), no further configuration of the /etc/multipath.conf file isrequired.Otherwise, create the /etc/multipath.conf file and add an appropriate device entry for yourstorage subsystem. See /usr/share/doc/packages/multipath-tools/multipath.conf.annotated for a template with extensive comments.After having set up the configuration, you can perform a “dry-run” with multipath -v2 -d,which scans the devices, then displays what the setup would look like. The output is similar to thefollowing:3600601607cf30e00184589a37a31d911[size=127 GB][features="0"][hwhandler="1emc"]\_ round-robin 0 [first]\_ 1:0:1:2 sdav 66:240 [ready ]\_ 0:0:1:2 sdr 65:16 [ready ]\_ round-robin 0\_ 1:0:0:2 sdag 66:0 [ready ]\_ 0:0:0:2 sdc 8:32 [ready ]Paths are grouped into priority groups. Only one priority group is ever in active use. To model anactive/active configuration, all paths end up in the same group. To model active/passiveconfiguration, the paths that should not be active in parallel are placed in several distinct prioritygroups. This normally happens completely automatically on device discovery.The output shows the order, the scheduling policy used to balance I/O within the group, and thepaths for each priority group. For each path, its physical address (host:bus:target:lun), device nodename, major:minor number, and state is shown.5.8 Configuring User-Friendly Names in /etc/multipath.confThe default name used in multipathing is the UUID of the logical unit as found in the /dev/disk/by-id directory. You can optionally override this behavior with user-friendly names instead. User-friendly names can be set via the ALIAS directive in the multipath.conf file.IMPORTANT: We recommend that you do not use aliases for the root device, because the ability toseamlessly switch off multipathing via the kernel command line is lost because the device namesdiffer.For an example of multipath.conf settings, see the /usr/share/doc/packages/multipath-tools/multipath.conf.synthetic file.1 In a terminal console, log in as the root user.2 Enter the following command (all on one line, of course):