Installation guide

Configuring persistent storage in Red Hat Enterprise Linux 6
245
KERNEL=="sd*", SUBSYSTEM=="block", PROGRAM="/sbin/scsi_id --whitelisted --replace-
whitespace /dev/$name", RESULT=="1IET_00010003", NAME="rack4row16lun3"
The udev daemon now searches all devices named /dev/sd* for a matching UUID in the rules.
When a matching device is connected to the system the device is assigned the name from the
rule. For example:
# ls -la /dev/rack4row16*
brw-rw---- 1 root disk 8, 18 May 25 23:35 /dev/rack4row16lun1
brw-rw---- 1 root disk 8, 34 May 25 23:35 /dev/rack4row16lun2
brw-rw---- 1 root disk 8, 50 May 25 23:35 /dev/rack4row16lun3
5. Copy the changes in /etc/scsi_id.config and /etc/udev/rules.d/20-names.rules to
all relevant hosts.
Networked storage devices with configured rules now have persistent names on all hosts where the
files were updated This means you can migrate guests between hosts using the shared storage and
the guests can access the storage devices in their configuration files.
Multiple path configuration
The multipath package is used for systems with more than one physical path from the computer
to storage devices. multipath provides fault tolerance, fail-over and enhanced performance for
network storage devices attached to Red Hat Enterprise Linux 6 systems.
Implementing LUN persistence in a multipath environment requires defined alias names for your
multipath devices. Each storage device has a UUID, also known as a World Wide Identifier or WWID,
which acts as a key for the aliased names.
This procedure implements LUN device persistence using the multipath daemon.
1. Determine the World Wide Identifier of each device using the scsi_id --whitelisted --
replace-whitespace --device=/dev/sd* command:
# scsi_id --whitelisted --replace-whitespace --device=/dev/sde
1IET_00010004
# scsi_id --whitelisted --replace-whitespace --device=/dev/sdf
1IET_00010005
# scsi_id --whitelisted --replace-whitespace --device=/dev/sdg
1IET_00010006
# scsi_id --whitelisted --replace-whitespace --device=/dev/sdh
1IET_00010007
2. Create the multipath configuration file, /etc/multipath.conf. In it create a defaults
section, and disable the user_friendly_names option unless you have a specific need for it.
It is also a good idea to configure the default arguments for the getuid_callout option. This is
generally a useful start:
defaults {
user_friendly_names no
getuid_callout "/sbin/scsi_id --whitelisted --replace-whitespace --device=/dev/%n"
}
3. Below the defaults section add a multipaths section (note the plural spelling). In this section
add each of the WWIDs identified from the scsi_id command above. For example:
multipaths {