Convert volume group vg1 from LVM1 metadata format to the new LVM2
vgconvert -M2 vg1
Use pvscan(8) to see which PVs lost their metadata.
Run pvcreate(8) with the --uuid and --restorefile options on each
such PV to reformat it as it was, using the archive file that
vgconvert(8) created at the start of the procedure.
Finally run vgcfgrestore(8) with that archive file to restore
the original metadata.