What I would probably do is:
- install new disk alongside the old one
- put one big partition on the new disk and pvcreate the partition
- vgextend the existing VG with the new partition
- vgreduce the VG, removing the old disk's partitions
That should be just as fast as dd'ing the old filesystems and can be
done without downtime. You don't need to resize any existing partitions,
but you can of course grow the LVs and the filesystems afterwards, if
you want to take advantage of the additional space.