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Introduction to LVM
Let’s discuss LVM first. Using LVM terminology, a virtual partition is a logical volume, which is part of a volume group, or an association of several physical volumes. Physical volumes are real partitions (or virtual partitions exported by other abstractions, such as a software RAID device or an encrypted partition).
With its lack of distinction between “physical” and “logical” partitions, LVM allows you to create “virtual” partitions that span several disks. The benefits are twofold: the size of the partitions is no longer limited by individual disks but by their cumulative volume, and you can resize existing partitions at any time, such as after adding an additional disk.
This technique works in a very simple way: each volume, whether physical or logical, is split into blocks of the same size, which LVM correlates. The addition of a new disk will cause the creation of a new physical volume providing new blocks that can be associated to any volume group. All of the partitions in the volume group can then take full advantage of the additional allocated space.