Storix Software SBAdmin Device-Mapper Multipath Devices - Manual (Page 2)

Storix System Backup Administrator 2 Device-Mapper Multipath Guide
Copyright © 2014 Storix, Inc.
Storix is a registered trademark of Storix, Inc in the USA. SBAdmin is a trademark of Storix, Inc in the USA and other countries
SBAdmin and DM-Multipath Guide
The purpose of this guide is to provide the steps necessary to use SBAdmin in an environment where SAN
storage is used in conjunction with device-mapper multipath devices. When a system is using dm-multipath
devices, there are several considerations that need to be addressed. The device naming, tools available, and
device modules loaded become critical issues in discovery of devices and recreation of those devices upon
restore. The information in this guide should provide the necessary information to create backups from systems
using dm-multipath devices or for users who want to migrate a system backup to multipath devices. This guide
is not intended to assist users in the initial setup of dm-multipath devices. For information on initially setting up
dm-multipath devices, contact your Linux OS support vendors directly.
Requirements for DM-Multipath support
Software requirements
Support for dm-multipath devices has been available to Linux users for a few years, however, how the
devices are created and supported by distributions has changed greatly over time as the technology
matures. Below is the minimal level of the tools and file sets that SBAdmin has tested and will support.
dm-multipath-tools version 0.4.5 (also known as device-mapper-multipath)
device-mapper version 1.02
udev version 039-10
Device detection requirements
Device naming
If you plan on creating backups from a system using dm-multipath devices, the SBAdmin software must be
able to recognize those devices prior to creating the backup. There are a number of ways your multipath
devices can be named (WWID, dm-[0-9], mpath[a-z], mpath[0-9], etc). How the devices are named depends
on three factors: The “user_friendly_names” setting in /etc/multipath.conf, aliases setup in
/etc/multipath.conf and UDEV rules.
One requirement for dm-multipath support with SBAdmin is the setting “user_friendly_names yes” in
/etc/multipath.conf.
Another requirement is a UDEV rule in place that creates a symbolic link from the device node to the device
in /dev/mpath. Some Linux distributions already create these links. If your Linux distribution does not,
SBAdmin has a sample UDEV rule that you may apply. It is designed to create the proper links and allow
SBAdmin to discovery the devices. This rule may be found as /opt/storix/config/dm_mpath_udev_rule. To
apply the rule to your system:
1. Copy the rule into place
# cp /opt/storix/config/dm_mpath_udev_rule /etc/udev/rules.d/99-storixmpath.rules
2. Trigger the UDEV rule with one of the following commands (depending on your version of UDEV)
# udevadm trigger
# udevtrigger