When your data needs grow for a volume, you might need to increase the amount of space allocated to its file system.
Section 5.1, Guidelines for Resizing
Section 5.2, Increasing the Size of an Ext2, Ext3, or Ext4 File System
Section 5.3, Increasing the Size of a Reiser File System
Section 5.4, Decreasing the Size of an Ext2 or Ext3 File System
Section 5.5, Decreasing the Size of a Reiser File System