Follow Techotopia on Twitter

On-line Guides
All Guides
eBook Store
iOS / Android
Linux for Beginners
Office Productivity
Linux Installation
Linux Security
Linux Utilities
Linux Virtualization
Linux Kernel
System/Network Admin
Programming
Scripting Languages
Development Tools
Web Development
GUI Toolkits/Desktop
Databases
Mail Systems
openSolaris
Eclipse Documentation
Techotopia.com
Virtuatopia.com
Answertopia.com

How To Guides
Virtualization
General System Admin
Linux Security
Linux Filesystems
Web Servers
Graphics & Desktop
PC Hardware
Windows
Problem Solutions
Privacy Policy

  




 

 

25.12. Configuring LUN Persistence

This section covers how to implement LUN persistence in guests and on the host machine with and without multipath.
Implementing LUN persistence without multipath
If your system is not using multipath, you can use udev to implement LUN persistence. Before implementing LUN persistence in your system, ensure that you acquire the proper UUIDs. Once you acquire these, you can configure LUN persistence by editing the scsi_id file that resides in the /etc directory. Once you have this file open in a text editor, you must comment out this line:
# options=-b
Then replace it with this parameter:
# options=-g
This tells udev to monitor all system SCSI devices for returning UUIDs. To determine the system UUIDs, use the scsi_id command:
# scsi_id -g -s /block/sdc
*3600a0b80001327510000015427b625e*
The long string of characters in the output is the UUID. The UUID does not change when you add a new device to your system. Acquire the UUID for each the device in order to create rules for the devices. To create new device rules, edit the 20-names.rules file in the /etc/udev/rules.d directory. The device naming rules follow this format:
# KERNEL="sd*",  BUS="scsi",  PROGRAM="sbin/scsi_id", RESULT="
UUID
", NAME="
devicename
"
Replace your existing UUID and devicename with the above UUID retrieved entry. The rule should resemble the following:
KERNEL="
sd*
",  BUS="scsi",  PROGRAM="sbin/scsi_id", RESULT="
3600a0b80001327510000015427b625e
", NAME="
mydevicename
"
This enables all devices that match the /dev/sd* pattern to inspect the given UUID. When it finds a matching device, it creates a device node called /dev/devicename . For this example, the device node is /dev/mydevice . Finally, append the /etc/rc.local file with this line:
/sbin/start_udev
Implementing LUN persistence with multipath
To implement LUN persistence in a multipath environment, you must define the alias names for the multipath devices. For this example, you must define four device aliases by editing the multipath.conf file that resides in the /etc/ directory:
multipath  {  
             wwid       3600a0b80001327510000015427b625e
             alias      oramp1
}
multipath  {  
             wwid       3600a0b80001327510000015427b6
             alias      oramp2
}
multipath  {  
             wwid       3600a0b80001327510000015427b625e
             alias      oramp3
}
multipath  {  
             wwid       3600a0b80001327510000015427b625e
             alias      oramp4
}
This defines 4 LUNs: /dev/mpath/oramp1, /dev/mpath/oramp2, /dev/mpath/oramp3, and dev/mpath/oramp4. The devices will reside in the /dev/mpath directory. These LUN names are persistent over reboots as it creates the alias names on the wwid of the LUNs.

 
 
  Published under the terms of the GNU General Public License Design by Interspire