VERITAS Volume Manager 4.1 Migration Guide

Converting LVM to VxVM
Converting LVM Volume Groups to VxVM Disk Groups
Chapter 2 9
CAUTION Before you do the backup, you should carefully review “9. Implementing
changes for new VxVM logical volume names” on page 14. Backup processes
and systems themselves may have dependencies on the volume names
currently in use on your system. The conversion to VxVM changes those names.
You are advised to understand the implications name changes have for
restoring from the backups you are about to make.
File system back up of user data You can use the backup utility that you normally use to back
up data on your logical volumes. For example, to back up logical volumes that contain file
systems, the fbackup (1M) command can be used to back up the data to tape.
For example, to backup the data on /dev/vg01/lvol3 mounted on /foodir, use the
following command:
# fbackup -0i /foodir -f /dev/rmt/c0t0d0BEST
Non-file system back up If a logical volume you are converting does not contain a file system,
and is being used directly by an application (such as a database application), use the backup
facilities provided by the application. If no such facility exists, consider using the dd
command.
5. Planning for new VxVM logical volume names
When you change from LVM volumes to VxVM volumes, the device names by which your
system accesses data are changed. LVM creates device nodes for its logical volumes in /dev
under directories named for the volume group. VxVM creates its device nodes in /dev/vx/dsk
and /dev/vx/rdsk. When conversion is complete, the old LVM device nodes are gone from the
system, and the system will access data on the device nodes in /dev/vx.
This change in names can present problems. Any application that refers to specific device
node names will be at risk when these names change. Similarly, any files that record specific
device node names for use by applications can be problematic.
The most obvious area where this problem arises is in /etc/fstab. To handle this problem,
vxvmconvert will rewrite the fstab with the new VxVM names when conversion is done so
that fsck, mount, and related utilities will behave as they did prior to the conversion.
There are potentially many other applications, though, that may be put at risk by the name
changes in conversion. vxvmconvert cannot help with these. The system administrator must
examine the mechanisms used in each of the following areas to see if they reference LVM
device names:
• Databases run on raw logical devices may record the name of that device node.
• Backup systems may do device level backups based on device node names recorded in
private files. Also labeling of the backups may record device names.