Logical Volume Management, LVM, is a newer alternative to hard partitioning of a hard drive.

Advantages include : --

File systems can extend over more than one physical hard drive.

Additional physical hard drives can be added to the system at any time.

Logical volumes can be more easily managed, extending them when required, migrating them to another system, or retiring an ailing physical volume and replacing it with a new drive.

Disadvantages include : --

There is a fairly steep learning curve to get into this new, for me, technology.

There are three basic layers to the LVM system.

1. Physical Extents
   
   These are physical drives or partitions that are available to the LVM system.
   
   
2. Volume Groups
   
   These are groupings that tie together the physical extents and the logical volumes that reside thereon.
   
   
3. Logical Volumes
   
   These are similar to normal partitions in that they are formatted with some file system, such as ext3, ext4 or btrfs using normal formatting tools. 
   
   They are dissimilar to normal partitions in that they can be more easily managed, including extending, reducing, moving from one physical extent to another or simply deleted and the space regained can be absorbed into another logical volume.
   
   

The procedure for setting up an LVM system is like this.

First identify some free space on at least one physical hard drive.