Database Reference
In-Depth Information
Or install it manually:
rpm -ivh device-mapper-multipath-0.4.9-56.el6_3.1.x86_64.rpm
To configure the multipath driver to combine these I/O paths into a pseudo-device, you need to add related entries
to the multipathing driver configuration file /etc/multipath.conf. This is an example of the /etc/multipath.conf file:
defaults {
udev_dir /dev
polling_interval 5
path_selector "round-robin 0"
path_grouping_policy failover
getuid_callout "/lib/udev/scsi_id --whitelisted --device=/dev/%n"
prio const
path_checker directio
rr_min_io 1000
rr_weight uniform
failback manual
no_path_retry fail
user_friendly_names yes
}
...
multipaths {
multipath {
wwid 36842b2b000742679000007a8500b2087 #<---sdc and sde
alias ocrvoting
}
multipath {
wwid 36842b2b000742679000007a5500b1cd9 #<--- sdd and sdf
alias data
}
}
...
Start the multipath service:
# service multipathd start
Starting multipathd daemon: [ OK ]
The device-mapper-multipath daemon creates a pseudo-device 'ocrvoting':
[oracle@k2r720n1 ~]$ ls -l /dev/mapper/
lrwxrwxrwx 1 root root 7 Oct 29 06:33 /dev/mapper/data -> ../dm-9
lrwxrwxrwx 1 root root 7 Oct 29 06:33 /dev/mapper/ocrvoting -> ../dm-8
This shows that the soft links such as /dev/mapper/data pointing to block device /dev/dm-9
In addition to the benefit of combining multipath devices into a single pseudo-device, the multipath driver also
creates a consistent device name. In Linux, by default the device name of storage LUN may not guarantee consistency
every time the OS gets rebooted. For example, for the same LUN, /dev/sdc may be changed to /dev/sdd the next time
the OS gets rebooted. This can create a serious problem if the RAC Database uses this volume to store the database
files, as the RAC Database instance recognizes the volume by name. If the name changes, this volume cannot be
found again. And in the Oracle RAC environment, we also need to make sure the same shared storage LUN has the
