What Is Logical Volume Management?

T.S. Adams

Partitioning a drive is dividing the drive into different logical segments. One common example of this used by modern computer manufacturers is creating a "C" drive for basic files and a "D" drive for system recovery files. Logical volume management (LVM) does away with the concept of partitioning by utilizing the hard drive as it was intended, as a single unit for data storage.

Logical volume management uses the hard drive as a single unit of storage.
Logical volume management uses the hard drive as a single unit of storage.

Think of partitioning as drawing lines on a map marking a country's sovereign territory. Once these lines are drawn they can be changed, but the process is generally difficult. For partitioned systems, changing the size and makeup of partitions requires re-formatting, which can be a drastic step. During re-formatting, all data stored on the selected partition is erased, and the partition is redrawn to the new specifications.

Logical volume management offers an alternative. On a system utilizing logical volume management, the concept of dividing partitions on a disk becomes much more fluid. On an LVM system, partitions can be merged, combined, and re-sized, all without reformatting any of the space on the disk.

This improves the fluidity and usefulness of computer data storage systems. Changing one's mind regarding a data storage scheme on a logical volume management system is simple, and redistributing data does not require wiping the drive and beginning over. However, logical volume management systems are not without drawbacks.

Two major drawbacks to logical volume systems are fragmentation and impaired recovery. Files stored on a hard drive are not always stored in a single chunk. More often, the computer breaks up the files into parts and stores each part into available gaps on the drive. This is fragmentation: since all of the files for a particular program are not kept together, retrieving those files becomes more difficult, slowing down performance.

Recovery problems occur because the data on LVM volumes is so fluid, it becomes much more difficult to reassemble information on the drive following a crash. This means that although they are more fluid, LVM volumes are also more volatile. As a result, backup solutions become that much more important when dealing with LVM systems.

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