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5.7 Adding Support for the Storage Subsystem
to /etc/multipath.conf
If you are using a storage subsystem that is automatically detected (see
“Supported Storage
Subsystems” on page 46
), no further configuration of the
/etc/multipath.conf
file is
required.
Otherwise, create the
/etc/multipath.conf
file and add an appropriate device entry for your
storage 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 the
following:
3600601607cf30e00184589a37a31d911
[size=127 GB]
[features="0"]
[hwhandler="1
emc"]
\_ 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 an
active/active configuration, all paths end up in the same group. To model active/passive
configuration, the paths that should not be active in parallel are placed in several distinct priority
groups. 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 the
paths for each priority group. For each path, its physical address (host:bus:target:lun), device node
name, major:minor number, and state is shown.
5.8 Configuring User-Friendly Names in /etc/
multipath.conf
The 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 to
seamlessly switch off multipathing via the kernel command line is lost because the device names
differ.
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):
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