VERITAS Volume Manager 3.5 Migration Guide (September 2004)

Chapter 2
Converting LVM to VxVM
Converting LVM Volume Groups to VxVM Disk Groups
16
• 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.
A 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.
Over time, the ultimate goal should be that the underlying VxVM naming is used by all applications, and that
there are no indirect references to those volumes.
6. Stopping application access to volumes in the volume group to be converted
No applications can be active on the LVM volume group undergoing conversion. Before attempting to convert
any volume group, you must ensure that applications using that group are down. This involves stopping
databases, unmounting file systems, etc.
NOTE If you are converting a volume with swap space on it, the conversion requires a reboot. The
swap space cannot be taken out of control of the operating system with a shutdown to single
user mode.
As described in “Conversion and Reboot” on page 17, vxvmconvert tries to unmount mounted file systems
during the conversion. Bear in mind though, that vxvmconvert makes no attempt to close down running
applications on those file systems, nor does it attempt to deal with applications (e.g., databases) running on
raw LVM volumes.
NOTE It is strongly recommended that you do not rely on vxvmconvert's mechanisms for unmounting
file systems. Conversion will be simpler if you close applications, and unmount file systems
before running vxvmconvert.
To unmount a file system, use the following command: