Configuration File Devices - Red Hat DEVICE-MAPPER MULTIPATH 5.2 Configuration And Administration Manual

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5. Configuration File Devices

Table 4.3, "Device Attributes"
device in the
devices
used by DM-Multipath unless they are overwritten by the attributes specified in the
section of the
multipath.conf
the attributes set in the
Many devices that support multipathing are included by default in a multipath configuration. The
values for the devices that are supported by default are listed in the
file. You probably will not need to modify the values for these devices, but if you do you can
overwrite the default values by including an entry in the the configuration file for the device that
overwrites those values. You can copy the device configuration defaults from the
multipath.conf.defaults
To add a device to this section of the configuration file that is not configured automatically by
default, you need to set the
looking at
/sys/block/device_name/device/vendor
/sys/block/device_name/device/model
as in the following example:
[root@cypher-06 ~]# cat /sys/block/sda/device/vendor
WINSYS
[root@cypher-06 ~]# cat /sys/block/sda/device/model
SF2372
The additional parameters to specify depend on your specific device. If the device is
active/active, you will usually not need to set additional parameters. You may want to set
path_grouping_policy
and
no_path_retry rr_min_io
If the device is active/passive, but it automatically switches paths with I/O to the passive path,
you need to change the checker function to one that does not send IO/ to the path to test if it is
working (otherwise, your device will keep failing over). This almost always means that you set
the to
path_checker tur
command, which most do.
If the device needs a special command to switch paths, then configuring this device for
multipath requires a hardware handler kernel module. The current hardware handlers are
and " . If these are not sufficient for your device, you may not be able to configure the
rdac
shows the attributes that you can set for each individual storage
section of the
multipath.conf
file for paths that contain the device. These attributes override
section of the
defaults
file for the device and override the values that you want to change.
and
vendor product
where
to . Other parameters you may need to set are
multibus
, as described in
; this works for all SCSI devices that support the Test Unit Ready
Configuration File Devices
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priorities
configuration file. These attributes are
file.
multipath.conf
multipath.conf.defaults
parameters. You can find these values by
and
is the device to be multipathed,
device_name
Table 4.3, "Device Attributes".
multipaths
emc
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