VERITAS Volume Manager 5.0 Migration Guide (September 2006)

24 Converting LVM to VxVM
Converting LVM volume groups to VxVM disk groups
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.
■ Scripts run by cron(1M).
■ Other administrative scripts.
Workaround
vxvmconvert records a mapping between the names of the LVM device nodes and
VxVM device nodes. This data can be used to create symbolic links from the old LVM
volume to the new VxVM device names. The mapping is recorded in the file:
/etc/vx/reconfig.d/vgrecords/vol_grp_name/vol_grp_name.trans
This file provides information on how to proceed further to link the old LVM volume
names to the new VxVM device names.
Caution: This method of resolving the naming problem has risks. The symbolic links can
become stale. For example, if a database refers to
/dev/vx/rdsk/vol1 through a
symbolic link
/dev/vg00/rvol1(“the old LVM name)”, and if the underlying VxVM
volume configuration is changed in any way, the database could refer to a missing or
different volume.
Note: You may want to use this symbolic link approach to ease the transition to VxVM.
You can set up the symbolic links after the successful conversion to VxVM. Then, you can
do the investigation on a case by case basis for each volume. Once you are satisfied that
there are no problems introduced by the name change, the symbolic link to that volume
can be removed. You must be careful to maintain a static VxVM volume configuration
during this transition period.