Red Hat LINUX VIRTUAL SERVER 4.7 - ADMINISTRATION Guide d'installation télécharger pdf (Page 30)

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:

[root@cypher-06 ~]# cat /sys/block/sda/device/vendor

WINSYS

[root@cypher-06 ~]# cat /sys/block/sda/device/mo del

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

m ultibus. 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). T his almost always means that you set the

path_checker to tur; this works for all SCSI devices that support the T est 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. T he current hardware handlers are em c and "rdac. If

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

Chapter 4. The DM-Multipath Configuration File

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Red Hat LINUX VIRTUAL SERVER 4.7 - ADMINISTRATION Guide d'installation Page 30