DM-Multipath Guide Version 8.
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.
SBAdmin will refer to all multipath devices with the path /dev/mpath/mpathX. If your backups do not appear to include the data residing on your dm-multipath devices, verify that the devices are seen in the /dev/mpath directory. Having the devices in the /dev/mpath directory is required for device discovery. However, there are other factors that can prevent device detection.
underlying path device as the block special device used for mounting the filesystem. This causes problems when the software attempts to query the device for size and geometry. The block special device listed in the /etc/fstab file should be the dm-multipath device instead of an underlying path device. Verify that if your /etc/fstab file is using the /dev/disk/by-uuid/* naming convention, that you change the entries to the dmmultipath device name or the /dev/disk/by-name/* naming convention.
After loading the module for the HBA, only the underlying paths are listed and no dm-multipath devices were created. At this point it is necessary to also load the device handler for the SAN. Now the list of devices created also shows the dm-multipath devices that were created and available for use during the restore. Storix System Backup Administrator 5 Device-Mapper Multipath Guide Copyright © 2014 Storix, Inc. Storix is a registered trademark of Storix, Inc in the USA.
Troubleshooting Because there are several device naming schemes possible when using dm-multipath devices (see the section titled “Device naming” above), it may be necessary to create a custom version of the device_info file that is used as a reference for device naming schemes. If the restore fails because your partitions are not discovered during install, reboot from the boot media and customize the /opt/storix/config/device_info file.
