Red Hat GNBD WITH GLOBAL FILE SYSTEM IN RHEL 4.5 Instalační příručka stáhnout pdf (Strana 31)

Configuration File Devices

rr_weight priorities

no_path_retry 5

}

multipath {

wwid 1DEC_____321816758474

alias red

rr_weight priorities

}

4.5. Configuration File Devices

Table 4.3, “Device Attributes” shows the attributes that you can set for each individual storage device

in the devices section of the multipath.conf configuration file. These attributes are used by DM-

Multipath unless they are overwritten by the attributes specified in the multipaths section of the

multipath.conf file for paths that contain the device. These attributes override the attributes set in

the defaults section of the multipath.conf file.

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 multipath.conf.defaults 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 configuration file for the device that overwrites those values.

You can copy the device configuration defaults from the multipath.conf.defaults file for the

device and override the values that you want to change.

To add a device to this section of the configuration file that is not configured automatically by default,

you need to set the vendor and product parameters. You can find these values by looking at /sys/

block/device_name/device/vendor and /sys/block/device_name/device/model where

device_name is the device to be multipathed, as in the following example:

# cat /sys/block/sda/device/vendor

WINSYS

# 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

to multibus. Other parameters you may need to set are no_path_retry and rr_min_io, as

described in Table 4.3, “Device Attributes”.

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 I/O to the path to test if it is

working (otherwise, your device will keep failing over). This almost always means that you set the

path_checker to tur; this works for all SCSI devices that support the Test Unit Ready 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 emc and rdac. If

these are not sufficient for your device, you may not be able to configure the device for multipath.

Table 4.3. Device Attributes

Attribute Description

vendor Specifies the vendor name of the storage device to which the

device attributes apply, for example COMPAQ.

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