You need to be especially careful on SPARC systems where the disks have Sun disk labels on them.
The normal layout for a Sun disk label is for the first partition to start at block zero of the disk, thus the first partition also covers the area containing the disk label itself. This works fine for ext2 filesystems (and is essential for booting using SILO) but such partitions should not be used for LVM. This is because LVM starts writing at the very start of the device and will overwrite the disk label.
If you want to use a disk with a Sun disk label with LVM, make sure that the partition you are going to use starts at cylinder 1 or higher.