Logical Volume Manager (Lvm); What Is Lvm - Red Hat ENTERPRISE LINUX 3 System Administration Manual

Chapter 4.

Logical Volume Manager (LVM)

4.1. What is LVM?

LVM is a method of allocating hard drive space into logical volumes that can be easily resized instead
of partitions.
With LVM, the hard drive or set of hard drives is allocated to one or more physical volumes. A physical
volume can not span over more than one drive.
The physical volumes are combined into logical volume groups, with the exception of the
/boot/
partition. The partition can not be on a logical volume group because the boot loader can not
/boot/
read it. If the root partition is on a logical volume, create a separate partition which is not a
/ /boot/
part of a volume group.
Since a physical volume can not span over more than one drive, to span over more than one drive,
create one or more physical volumes per drive.
Physical Volume Physical Volume Physical Volume /boot
9.1 GB 9.1 GB 9.1 GB 75 MB (ext3)
Logical Volume Group
(9.1 GB x 3) - 75 MB
Figure 4-1. Logical Volume Group
The logical volume group is divided into logical volumes, which are assigned mount points such as
and and file system types such as ext3. When "partitions" reach their full capacity, free space
/home /
from the logical volume group can be added to the logical volume to increase the size of the partition.
When a new hard drive is added to the system, it can be added to the logical volume group, and the
logical volumes that are the partitions can be expanded.