In this tutorial we want to replace /dev/sdc1 with /dev/sdd1. Read on.

1. prepare the disk for lvm:

jupiter:~# pvcreate /dev/sdd1
  Physical volume "/dev/sdd1" successfully created

2. add the disk in the volume group:

jupiter:~# vgextend squidvg /dev/sdd1
  Volume group "squidvg" successfully extended
jupiter:~# pvscan | grep squidvg
  PV /dev/sdc1   VG squidvg   lvm2 [30.00 GiB / 5.00 GiB free]
  PV /dev/sdd1   VG squidvg   lvm2 [30.00 GiB / 30.00 GiB free]

3. Now we need to move the data from one disk to another and we can do with pvmove command.

jupiter:~# lvscan | grep squidvg
  ACTIVE            '/dev/squidvg/cache' [25.00 GiB] inherit
jupiter:~# pvmove -n cache /dev/sdc1 /dev/sdd1
  /dev/sdc1: Moved: 0.0%
  /dev/sdc1: Moved: 2.3%
  /dev/sdc1: Moved: 3.8%
  /dev/sdc1: Moved: 5.3%
[..cut useless output..]
  /dev/sdc1: Moved: 98.0%
  /dev/sdc1: Moved: 98.9%
  /dev/sdc1: Moved: 100.0%
jupiter:~# pvscan | grep squidvg
  PV /dev/sdc1   VG squidvg   lvm2 [30.00 GiB / 30.00 GiB free]
  PV /dev/sdd1   VG squidvg   lvm2 [30.00 GiB / 5.00 GiB free]

4. Remove the disk from volume group and lvm:

jupiter:~# vgreduce squidvg /dev/sdc1
  Removed "/dev/sdc1" from volume group "squidvg"
jupiter:~# pvremove /dev/sdc1 
  Labels on physical volume "/dev/sdc1" successfully wiped

And that is it!