VERITAS Volume Manager 3.5 Migration Guide (September 2004)

Chapter 2

Converting LVM to VxVM

Converting LVM Volume Groups to VxVM Disk Groups

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 11.

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.

Sample examples of the analyze option are shown in “Examples” on page 22.

3. Taking actions to make conversion possible if analysis fails

Analysis may fail for any of the reasons listed in the section “Volume Group Conversion Limitations” on

page 11”.

Messages from vxvmconvert will explain the type of failure and any actions that can be taken before retrying

the analysis. Refer to Appendix A, “Conversion Error Messages,” on page 57 for complete details of speciﬁc

error messages and actions.

4. Backing up your LVM conﬁguration and user data

After analysis you know which volume group or groups you want to convert to VxVM disk groups. Up to this

point, you have not altered your LVM conﬁguration.

By taking the next step (completing the conversion to VxVM), you are signiﬁcantly changing access to your

storage.

Although the conversion process does not move, or in any other way affect user data, you are strongly

encouraged to back up all data on the affected disks. Similarly, you should back up the LVM conﬁguration

itself.

During a conversion, any spurious reboots, power outages, hardware errors or operating system bugs can

have unpredictable and undesirable consequences. You are advised to be on guard against disaster with a set

of veriﬁed backups.

Backing up an LVM conﬁguration Use the vgcfgbackup(1) utility before running vxvmconvert to save

a copy of the LVM conﬁguration.

You can back up the LVM volumes using the following command:

# vgcfgbackup -f

pathname/filename vol_grp_name

Be sure to use the -f option to save the data into a ﬁle other than the default. vxvmconvert uses LVM

utilities which themselves save the conﬁguration using vgcfgbackup. If you do not use the -f option when

you attempt to backup the conﬁguration, the conversion process will overwrite your attempted backup.