VERITAS Volume Manager 3.5 Migration Guide (September 2004)

Chapter 2

Converting LVM to VxVM

Converting LVM Volume Groups to VxVM Disk Groups

A copy of this LVM conﬁguration should be kept off-line on tape or some other medium for use in the event of

a disaster during conversion.

For example, to put a copy on tape, use the following command:

# tar cvf /dev/rmt/c3t0d0BEST /vgbackups/vg08

NOTE The vxvmconvert utility itself also saves a snapshot of the LVM metadata in the process of

conversion for each disk. This data is saved in a different format from that of vgcfgbackup. It

can only be used via the vxvmconvert program. With certain limitations, you can reinstate the

LVM volumes after they have been converted to VxVM using this data. (See section “Example:

displaying the vxvmconvert menu” on page 22”.) Even though vxvmconvert provides this level

of backup of the LVM conﬁguration, you are advised to use vgcfgbackup before running

vxvmconvert.

Backing up user data To back up user data, use your regular backup processes.

CAUTION Before you do the backup, you should carefully review step “9. Implementing changes for new

VxVM logical volume names” on page 17. 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: