A volume manager is a virtualization technology that allocates space on mass storage devices. It offers greater flexibility than conventional disk partitioning, as it can combine, concentrate, or stripe stored data in a variety of ways, enabling system administrators to re-size or configure data in real-time without affecting system function.
Volume managers manage data in the following formats:
Physical volumes – these are hard disks or partitions of disks and external storage devices.
Physical extents – consecutive sequences of data that make up physical volumes
Logical extents that mirror physical extents
Volume groups that comprise multiple logical extents
By pooling the logical extents, a volume manager can create virtual disk partitions known as logical volumes of varying sizes. The volume manager can use the logical volumes in a variety of ways, including as swap storage or mounting filesystems on them.