Configuring Persistent Storage In Red Hat Enterprise Linux 5 - Red Hat ENTERPRISE LINUX 5 - VIRTUALIZATION GUIDE Manual

Chapter 8. Virtualized storage devices
8.3. Configuring persistent storage in Red Hat Enterprise
Linux 5
This section is for systems with external or networked storage; that is, Fibre Channel or iSCSI based
storage devices. It is recommended that those systems have persistent device names configured for
your hosts. This assists live migration as well as providing consistent device names and storage for
multiple virtualized systems.
Universally Unique Identifiers(UUIDs) are a standardized method for identifying computers and
devices in distributed computing environments. This sections uses UUIDs to identify iSCSI or Fibre
Channel LUNs. UUIDs persist after restarts, disconnection and device swaps. The UUID is similar to a
label on the device.
Systems which are not running multipath must use
Multiple path
multipath can use
Single path configuration
This procedure implements
which are not using multipath.
1. Edit the /etc/scsi_id.config file.
a. Ensure the options=-b is line commented out.
# options=-b
b. Add the following line:
options=-g
This option configures udev to assume all attached SCSI devices return a UUID.
2. To display the UUID for a given device run the scsi_id -g -s /block/sd* command. For
example:
# scsi_id --g --s -/block/sd*
3600a0b800013275100000015427b625e
The output may vary from the example above. The output displays the UUID of the device /dev/
sdc.
3. Verify the UUID output by the scsi_id -g -s /block/sd* command is identical from
computer which accesses the device.
4. Create a rule to name the device. Create a file named 20-names.rules in the /etc/udev/
rules.d directory. Add new rules to this file. All rules are added to the same file using the same
format. Rules follow this format:
KERNEL=="sd[a-z]", BUS=="scsi", PROGRAM="/sbin/scsi_id --g --s -/block/%k",
RESULT="UUID", NAME="devicename"
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configuration.
LUN
device persistence using udev. Only use this procedure for hosts
Single path configuration. Systems running