Add the new disk drive to the system, you need to reboot the machine and configure the hardware RAID if required.
Add the new disk to Volume group
For e.g.: if the disk is HP with Smart array
# pvcreate /dev/cciss/c0d1
# vgextend <volume_group_name> /dev/cciss/c0d1
Extend the Logical volume:
# lvextend -L<+mention_the_size> /dev/<volume_group>/<logical_volume>
eg: # lvextend -L+25G /dev/localhost/var
# lvextend -L+10G /dev/localhost/home
Resize the file system:
# resizefs <file_system>
eg:
# resizefs /dev/mapper/localhost-var
# resizefs /dev/mapper/localhost-home
./arun