LVM is a method of allocating hard drive space into logical volumes that
can be easily resized instead of partitions.
With LVM, a hard drive or set of hard drives is allocated to one or more
physical volumes. A physical volume cannot span
over more than one drive.
The physical volumes are combined into logical volume
groups, with the exception of the
/boot/ partition. The /boot/
partition cannot be on a logical volume group because the boot loader
cannot read it. If the root (/) partition is on a
logical volume, create a separate /boot/
partition which is not a part of a volume group.
Since a physical volume cannot span over multiple drives, to span
over more than one drive, create one or more physical volumes per drive.
The logical volume group is divided into logical
volumes, which are assigned mount points, such as
/home and /m and file system
types, such as ext2 or ext3. When "partitions" reach their full
capacity, free space 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 partitions that are logical volumes can be expanded.
On the other hand, if a system is partitioned with the ext3 file system,
the hard drive is divided into partitions of defined sizes. If a
partition becomes full, it is not easy to expand the size of the
partition. Even if the partition is moved to another hard drive, the
original hard drive space has to be reallocated as a different partition
or not used.
LVM support must be compiled into the kernel, and the default Red Hat
kernel is compiled with LVM support.
To learn how to configure LVM during the installation process, refer to
Chapter 8 LVM Configuration.
