VERITAS Volume Manager 5.0 Migration Guide (September 2006)

21Converting LVM to VxVM
Converting LVM volume groups to VxVM disk groups
Conversion steps explained
1. Identifying LVM disks and volume groups for conversion
The obvious first step in the conversion process is to identify what you want to convert.
The native LVM administrative utilities like
vgdisplay and SAM can help you identify
candidate LVM volume groups as well as the disks that comprise them.
You can also use the vxvmconvert and vxdisk commands to examine groups and their
member disks. The information presented through the
vxvmconvert and vxdisk utilities
and their interpretation is shown in “Examples” on page 31.
You can also list the LVM disks with the following VxVM command:
# vxdisk list
2. Analyzing an LVM volume group to see if conversion is possible
After you have selected a volume group for conversion, you need to analyze it to
determine if conversion for VxVM use is possible.
Use the analyze option of vxvmconvert to check for problems that would prevent the
conversion from completing successfully. This option checks for all the conditions listed
in “Volume group conversion limitations” on page 18.
The analysis calculates the space required to add the volume group disks to a VxVM disk
group, and to replace any existing disks and volumes with VxVM volumes, plexes, and
subdisks. If you don’t have the required space to convert the disks, the conversion would
fail.
Analysis can be run on a live system while users are accessing their data. To analyze LVM
volume groups, choose option 1 of the
vxvmconvert utility.
Note: The analysis option is presented as a separate menu item in vxvmconvert, but there
is an implicit analysis with any conversion. If you simply select the “Convert LVM
Volume Groups to VxVM” menu option,
vxvmconvert will go through analysis on any
group you specify. When you are using the convert option directly, you are given a chance
to abort the conversion after analysis, and before any changes are committed to disk. For
more information, see “Converting LVM volume groups to VxVM disk groups” on
page 17.
The analysis option is useful when you have a large number of groups/disks for
conversion and some amount of planning is needed before the actual conversion.
Installations with many users or critical applications can use the analyze option on a
running system. Then conversion downtime can be better planned and managed. Smaller
configurations may be better served by using the convert option directly while in a
downtime period.