Reducing and Increasing Logical Volumes in LVM

# lvscan
  ACTIVE            '/dev/DomUVol/lvol0' [200.00 GB] inherit
  ACTIVE            '/dev/xen-vm2/xen_prov2' [497.00 GB] inherit
  ACTIVE            '/dev/xen-vm1/xen_prov1' [499.00 GB] inherit


Below will reduce  /dev/xen-vm1/xen_prov1' [499.00 GB] inherit to just 30G

# lvreduce -L 30G /dev/xen-vm1/xen_prov1
  WARNING: Reducing active and open logical volume to 30.00 GB
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce xen_prov1? [y/n]: y
  Reducing logical volume xen_prov1 to 30.00 GB
  Logical volume xen_prov1 successfully resized


Now adding 400G to 30G


# lvextend -L+400G /dev/xen-vm1/xen_prov1
  Extending logical volume xen_prov1 to 430.00 GB
  Logical volume xen_prov1 successfully resized




# lvscan
  ACTIVE            '/dev/DomUVol/lvol0' [200.00 GB] inherit
  ACTIVE            '/dev/xen-vm2/xen_prov2' [497.00 GB] inherit
  ACTIVE            '/dev/xen-vm1/xen_prov1' [430.00 GB] inherit