LVM

http://tldp.org/HOWTO/LVM-HOWTO/


Ex:-

pvcreate /dev/hda5 /dev/hda6
vgcreate myvg /dev/hda5 /dev/hda6
vgdisplay
lvcreate -L +1900M -n mylv /dev/myvg
lvdisplay
mkfs -t ext3 /dev/myvg/mylv
mount

reducing the logical volume created:-

resize2fs /dev/myvg/mylv +1500M
e2fsck -f /dev/myvg/mylv
resize2fs /dev/myvg/mylv +1500M
lvreduce -L -1500M /dev/myvg/mylv

extending the logical volume created:-

lvextend -L +1500M /dev/myvg/mylv


adding new patition to the volume group myvg

vgextend myvg /dev/hda7

tested on Centos